The prevalence of and risk factors for atopy in early childhood: a whole population birth cohort study

Differential diagnosis of IgE-mediated allergy in young children with wheezing or eczema symptoms using a single blood test

BACKGROUND

Allergy-like symptoms are common in young children, but the case history and physical examination cannot identify the underlying origins of overlapping symptom profiles.

OBJECTIVE

To evaluate a blood test, Phadiatop Infant (Pharmacia Diagnostics AB, Uppsala, Sweden), for differentiating the capability of IgE-mediated disease in young children with recurrent wheezing, eczema, or both.

METHODS

One hundred forty-seven children (mean age, 2.0 years) were consecutively referred to 2 allergy centers by their primary care physician for recurrent wheezing, eczema, or both. The allergist's clinical evaluation included medical history, physical examination, skin prick testing with inhalant and food allergens, and specific IgE determinations in blood. The accuracy of Phadiatop Infant was evaluated in a masked manner against the allergist's final diagnosis.

RESULTS

Sixty-nine children had wheezing, 69 had eczema, and 9 had both symptoms. Sixty-one children were clinically diagnosed as having IgE-mediated allergy, 78 as having non-IgE-associated disease, and 8 as having an inconclusive diagnosis. Fifty-six of the 61 children with IgE-mediated allergy had positive Phadiatop Infant test results, and 64 of 78 without the condition had negative results. Sensitivity was 92% and specificity was 82%, with positive and negative predictive values of 80% and 93%, respectively. Thirteen children with a positive Phadiatop Infant test result and a negative final diagnosis were retested after 2 years; 12 of them were diagnosed as having IgE-mediated allergy using a masked evaluation.

CONCLUSIONS

The Phadiatop Infant blood test discriminates between IgE- and non-IgE-mediated symptoms in children younger than 4 years.

Allergen avoidance and prevention of atopy

PURPOSE OF REVIEW

Recent increases in the prevalence of atopic disease argue strongly that environmental factors operating primarily in early life play a significant role. Exposure to food and inhalant allergens early in life may constitute a risk factor amenable to manipulation.

RECENT FINDINGS

Recent observational and interventional studies have produced conflicting data regarding the effectiveness of allergen avoidance in primary and secondary prevention of atopic diseases.

SUMMARY

Exclusive breast feeding for 4-6 months may protect against the development of allergic diseases in early childhood and remains good advice. Convincing proof for the preventive effects of the delayed introduction of solid foods and hydrolyzed formula in formula-fed infants is lacking. There is some evidence to support a preventive effect of house dust mite allergen avoidance before sensitization occurs. The effect of exposure to animal allergen is uncertain, with some studies showing an increase in sensitization while others suggest a protective effect. Therefore, no evidence-based advice can be given at this stage regarding allergen avoidance measures to be adopted by families with infants at high risk of atopy, except perhaps to breast feed exclusively for at least 4 months. Data regarding the secondary prevention of allergic disease by allergen avoidance were more secure until the publication this year of two randomized controlled trials which suggest that mattress impermeable covers, the main dust mite allergen avoidance measure, may not work. Allergen avoidance, however, should remain an essential part of the management of allergic diseases, even if the benefit of mattress covers is in doubt.

Food allergy and atopic dermatitis in infancy: an epidemiologic study

Atopic dermatitis is common in infancy. The role of food allergy in atopic dermatitis of infancy is unclear. We examined the relationship between atopic dermatitis and immunoglobulin E (IgE)-mediated food allergy in infancy. A birth cohort of 620 infants with a family history of eczema, asthma, hayfever or immediate food allergy in a parent or sibling: 487 children had complete data including skin prick tests (SPTs) to evaluate IgE-mediated food allergy to cow milk, egg and peanut. Participants were grouped as no atopic dermatitis (Gp 0) or in quartiles of increasing severity of atopic dermatitis (Gps 1-4) quantified by days of topical steroid use as reported monthly. Adverse reactions to foods were recorded. The cumulative prevalence of atopic dermatitis was 28.9% to 12 months (10.3% of the cohort of moderate severity). As atopic dermatitis severity increased so did the prevalence of IgE-mediated food allergy (Gp 0, 40/346 vs. Gp 1, 6/36 vs. Gp 2, 8/35 vs. Gp 3, 12/35 vs. Gp 4, 24/35; chi(2) = 76; p < 10(-6)), and the frequency of reported adverse food allergy reactions (Gp 0, 43/346 vs. Gp 1, 4/36 vs. Gp 2, 8/35, vs. Gp 3, 5/35, vs. Gp 4, 13/35; chi(2) = 17; p = 0.002). The relative risk of an infant with atopic dermatitis having IgE-mediated food allergy is 5.9 for the most severely affected group. Atopic dermatitis is common in infancy. There is a strong association between IgE-mediated food allergy and atopic dermatitis in this age group.

Does maternal immunoglobulin E decrease with increasing order of live offspring? Investigation into maternal immune tolerance

BACKGROUND

Identifying the protective effect of a higher number of siblings is a significant finding in understanding the aetiology of allergic sensitization, asthma, eczema, and hayfever. Knowledge about causes behind the sibling effect may allow us to prevent atopic manifestations.

OBJECTIVE

We tested the hypothesis that rising order of live offspring increases maternal immune tolerance (immune non-reactivity) against allergens. To this end, we investigated whether maternal IgE levels are associated with the number of live offspring.

METHODS

In a cohort of 1456 newborns recruited between January 1989 and February 1990 on the Isle of Wight, UK, we determined maternal and cord serum IgE, and the order of live offspring. The data were analysed by means of linear and path analysis.

RESULTS

Maternal and cord serum IgE were available in 820 mother-infant pairs with birth order information. We found that the number of live offspring significantly reduces maternal IgE. The decline was more prominent in mothers with atopy (n=268). The geometric means of IgE after the first, second, and third or higher delivery were 74.4, 66.6, and 43.0 kU/L, respectively. Findings of path analysis suggest a significant direct effect of birth order on maternal IgE, but no direct effect of birth order on cord serum IgE.

CONCLUSION

The findings support that maternal immune tolerance against allergens may increase with increasing order of live offspring and thus pass on a lower risk of developing atopy in children of higher birth order.

Exposure to NO2 and nitrous acid and respiratory symptoms in the first year of life

BACKGROUND

Effects of nitrogen dioxide (NO2) on respiratory health have been the subject of extensive research. The outcomes of these studies were not consistent. Exposure to nitrous acid, which is a primary product of combustion, and is also formed when NO2 reacts with water, may play an important role in respiratory health. We estimate the independent effects of exposure to nitrogen dioxide and nitrous acid on respiratory symptoms during the first year of life.

METHODS

Nitrogen dioxide and nitrous acid concentrations were measured once (1996-1998) in the homes of 768 infants who were at risk for developing asthma. Infants were living in southern New England. The frequency of respiratory symptoms in these children was recorded during the first year of life.

RESULTS

Infants living in homes with an NO2 concentration exceeding 17.4 ppb (highest quartile) had a higher frequency of days with wheeze (rate ratio = 2.2; 95% confidence interval = 1.4-3.4), persistent cough (1.8; 1.2-2.7), and shortness of breath (3.1; 1.8-5.6) when compared with infants in homes that had NO2 concentrations lower than 5.1 ppb (lowest quartile), controlling for nitrous acid concentration. Nitrous acid exposure was not independently associated with respiratory symptoms.

CONCLUSIONS

Among infants at risk for developing asthma, the frequency of reported respiratory symptoms in the first year of life was associated with levels of NO2 not currently considered to be harmful.

Ratio of omega-6 to omega-3 fatty acids and childhood asthma

Asthma is a leading cause of morbidity for children and is a major public health problem in Australia. Ecological and temporal data suggest that dietary factors may have a role in recent increases in the prevalence of asthma.

AIM

The aim of conducting this study was to investigate whether childhood asthma was associated with the ratio of omega 6 (n-6) to omega 3 (n-3) fatty acids in the diet (n-6:n-3).

METHOD

The Western Australian Pregnancy Cohort Study is a prospective birth cohort of 2602 children. Using a nested case-control cross-sectional study design within this cohort, a group of children were identified as cases with current asthma at 6 or at 8 years of age or as controls with no asthma at 6 or at 8 years. Dietary details including n-6 and n-3 fatty acid intake data were collected by parent response to a questionnaire when the children were 8 years old. Logistical regression was used to compare quartiles of n-6:n-3 intake in cases and controls. Adjustment was made for covariates: gender, gestational age, breastfeeding, older siblings, maternal smoking during pregnancy, maternal age, maternal asthma, child's current age in months, body mass index, total energy intake, and antioxidant intake (vitamins A, C, E, and zinc).

RESULTS

A response rate of 83% was achieved by providing complete data from 335 children [49% cases with current asthma (n = 166), 51% controls (n = 169)]. Following adjustment for covariates the association between the ratio of n-6:n-3 fatty acids and risk for current asthma was statistically significant (p = 0.022).

CONCLUSION

We found evidence for a modulatory effect of the dietary n-6:n-3 fatty acid ratio on the presence of asthma in children. Our results provide evidence that promotion of a diet with increased n-3 fatty acids and reduced n-6 fatty acids to protect children against symptoms of asthma is warranted.

Atopic manifestations are more common in patients with Crohn disease than in the general population

BACKGROUND

The role of TNF-alpha in Crohn disease is now well established and anti-TNF-alpha is frequently used as a second- or third-line treatment. Tumor necrosis factor-alpha (TNF-alpha) is traditionally associated with macrophages but has recently also been found in mast cells of the ileal wall in patients with Crohn disease. As it is well known that mast cells and TNF-alpha play important roles in atopic manifestations like asthma, allergic rhinitis; and eczema the aim of this study was to investigate whether these are seen more commonly in Crohn patients than in the general population.

METHODS

Patients with Crohn disease (n = 308), aged 18-50 years, living in the Linköping region in southeast Sweden, were asked to answer a questionnaire regarding the presence of any kind of atopic manifestations. The questionnaire was also sent to 930 controls collected from the Southeastern Region Population Registry. The controls were matched according to age, sex, and place of residence.

RESULTS

The response rate among the Crohn patients was 91% (280/308) and among controls 84% (779/930). Eczema was a significantly more frequent manifestation, being almost twice as common in Crohn patients (27%) as in the general population (16%). Adjustment by logistic regression for place of residence, gender, age and coexistence of any other atopic manifestation did not change the odds ratios significantly.

CONCLUSION

Atopic manifestations as a group, and eczema as a single manifestation, are significantly more frequent in Crohn patients than in the general population.

Hypoallergenic formulas--when, to whom and how long: after more than 15 years we know the right indication!

Hypoallergenic formulas are processed by enzymatic hydrolysis of different protein sources such as bovine casein/whey and soy followed by further processing such as heat treatment and/or ultrafiltration, or they are based on amino acid mixtures. The products have been classified according to the degree of protein hydrolysis as 'extensively' or 'partially' hydrolysed protein products. Product properties may be characterized by biochemical techniques, and reduction of allergenicity may be assessed in vitro with various immunological methods, and in vivo with skin prick tests, patch tests and challenge tests. In vitro tests do not predict the allergenic effects in humans, and at present there is no evidence of a specific threshold of immunogenic protein. Only pure amino acid mixtures are considered to be nonallergenic. Other 'hypoallergenic' products contain residual allergenicity. At present, the potential of a product for treatment and prevention of food allergy can only be determined by clinical trials using scientifically appropriate standards. It has been recommended that dietary products for treatment of cow's milk protein allergy in infants should be tolerated by at least 90% (with 95% confidence) of infants with documented cow's milk protein allergy. Some extensively hydrolysed products and amino-acid-based products have met these criteria. Formulas intended for prevention should have a very low, if any, allergenic activity until otherwise proven. So far there are no firm criteria available for the design of hypoallergenic foods for prevention. Newborns included in prevention studies should be from high-risk families; they should be randomized at birth and fed the formula when supplements are needed for at least the first 4-6 months of life. Follow-up should be at least 18 months, and children should be investigated when symptoms appear. Validated clinical criteria, including controlled food challenges, should be used for diagnosis. Infants fed formulas that claim to prevent or delay allergy should have a statistically significant lower prevalence of allergy when compared with infants fed a standard cow's milk formula. Feeding high-risk infants a documented hypoallergenic formula combined with avoidance of solid foods during the first 4-6 months reduces the cumulative incidence of cow's milk protein allergy and atopic dermatitis as compared with a standard cow's-milk-based formula. Partially hydrolysed formulas may have an effect, though it seems to be less than that of extensively hydrolysed formulas at present. Thus, if exclusive breast-feeding for 4-6 months is not possible in high-risk infants, a documented hypoallergenic formula and avoidance of solid foods are recommended for the first 4 months of life.

Dietary prevention of allergic diseases in infants and small children. Part III: Critical review of published peer-reviewed observational and interventional studies and final recommendations

The role of primary prevention of allergic diseases has been a matter of debate for the last 40 years. In order to shed some light on this issue, a group of experts of the Section of Pediatrics EAACI reviewed critically the existing literature on the subject. An analysis of published peer-reviewed observational and interventional studies was performed following the statements of evidence as defined by WHO. The results of the analysis indicate that breastfeeding is highly recommended for all infants irrespective of atopic heredity. A dietary regimen is unequivocally effective in the prevention of allergic diseases in high-risk children. In these patients breastfeeding combined with avoidance of solid food and cow's milk for at least 4-6 months is the most effective preventive regimen. In the absence of breast milk, formulas with documented reduced allergenicity for at least 4-6 months should be used.

Characterisation of atopic and non-atopic wheeze in 10 year old children

BACKGROUND

Wheezing occurs in both atopic and non-atopic children. The characteristics of atopic and non-atopic wheeze in children at 10 years of age were assessed and attempts made to identify whether different mechanisms underlie these states.

METHODS

Children were seen at birth and at 1, 2, 4 and 10 years of age in a whole population birth cohort study (n = 1456; 1373 seen at 10 years). Information was collected prospectively on inherited and early life environmental risk factors for wheezing. Skin prick testing, spirometry, and methacholine bronchial challenge were conducted at 10 years. Wheezing at 10 years of age was considered atopic or non-atopic depending on the results of the skin prick test. Independent significant risk factors for atopic and non-atopic wheeze were determined by logistic regression.

RESULTS

Atopic (10.9%) and non-atopic (9.7%) wheeze were equally common at 10 years of age. Greater bronchial hyperresponsiveness (p<0.001) and airways obstruction (p = 0.011) occurred in children with atopic wheeze than in those with non-atopic wheeze at 10 years. Children with atopic wheeze more often received treatment (p<0.001) or an asthma diagnosis for their disorder, although current morbidity at 10 years differed little for these states. Maternal asthma and recurrent chest infections at 2 years were independently significant factors for developing non-atopic wheeze. For atopic wheeze, sibling asthma, eczema at 1 year, rhinitis at 4 years, and male sex were independently significant.

CONCLUSIONS

Non-atopic wheeze is as common as atopic wheeze in children aged 10 years, but treatment is more frequent in those with atopic wheeze. Different risk factor profiles appear relevant to the presence of atopic and non-atopic wheeze at 10 years of age.

Are maternal psychosocial factors associated with cord immunoglobulin E in addition to family atopic history and mother immunoglobulin E?

BACKGROUND

Atopy in maternal and family histories is known to be a risk factor for elevated umbilical cord immunoglobulin E (cIgE). However, the association between cIgE and psychosocial factors remains under investigation.

OBJECTIVE

To explore whether psychosocial factors in addition to atopy contribute to elevated cIgE.

METHODS

Four private maternity hospitals fitting the quantile levels of SO(2) in 2000 cooperated with us by recruiting participants for this study: pairs of mothers and neonates living within 3-km catchment areas of air-monitoring stations. We used a questionnaire to collect exposure data, and the Pharmacia UniCap IgE assay test system to determine the levels of IgE in gravidas and cord blood.

RESULTS

Between July 2001 and March 2003, 334 mother and neonate pairs participated in this study. The frequencies of sensitization, serum IgE (sIgE)>100 IU/mL, or cIgE> or =0.35 IU/mL were not different between the four different hospitals. By multi-variate logistic regression analysis adjusted for environmental factors, genetic factors, and psychosocial factors, the risk factors for elevated cIgE were being a male neonate (odds ratio (OR)=3.5, 95% confidence interval (CI)=[1.5, 8.5]), carpets at home (OR=3.0, 95% CI=[1.02, 8.4]), maternal allergy to dog dander (OR=9.7, 95% CI=[1.2, 98.8], maternal total serum IgE>100 IU/mL (OR=5.1, 95% CI=[2.2, 12.8]), maternal regularly/mostly/often self-reported nervousness (OR=4.0, 95% CI=[1.3, 12.8]), family income 11,574-17 361 US dollars/year (OR=3.7, 95% CI=[1.3, 11.5]), incense burning (OR=4.0, 95% CI=[1.4, 13.3]), and atopy in maternal grandparents (OR=4.8, 95% CI=[1.7, 14.0]). By principle component analysis and logistic regression, psychosocial stress (beta +/- standard error=0.26+/-0.13, P=0.04) was associated with increased cIgE.

CONCLUSION

Psychosocial factors are potentially important risk factors for elevated cIgE.

Endotoxin exposure and eczema in the first year of life

OBJECTIVE

Exposure to endotoxin in early life has been proposed as a factor that may protect against the development of allergic diseases such as eczema. The objective of this study was to examine the relation between endotoxin exposure in early life and eczema in the first year of life in children with parental history of asthma or allergies.

METHODS

This study used a prospective birth cohort study of 498 children who had a history of allergy or asthma in at least 1 parent and lived in metropolitan Boston. A subset of 401 living rooms had house dust samples adequate for analysis of endotoxin.

RESULTS

In multivariate analyses adjusting for gender, income, and season of birth, endotoxin levels in the living room at 2 to 3 months of age was inversely associated with physician- or nurse-diagnosed eczema in the first year of life (odds ratio [OR] for each quartile increment: 0.76; 95% confidence interval [CI]: 0.61-0.96). Exposure to a dog in the home at age 2 to 3 months was also inversely associated with eczema in the first year of life, but the CI widened when endotoxin was included in the multivariate model (OR: 0.54; 95% CI: 0.27-1.09). Other variables associated with eczema in the first year of life included paternal history of eczema (OR: 1.91; 95% CI: 1.03-3.55) and maternal specific immunoglobulin E positivity to > or =1 allergen (OR: 1.61; 95% CI: 1.01-2.56).

CONCLUSIONS

Among children with parental history of asthma or allergies, exposure to high levels of endotoxin in early life may be protective against eczema in the first year of life. In these children, paternal history of eczema and maternal sensitization to at least 1 allergen are associated with an increased risk of eczema in the first year of life.

Immune and histopathologic examination of flea bite-induced papular urticaria

BACKGROUND

Papular urticaria caused by flea bite presents clinical symptoms of hypersensitive reaction accompanied by skin lesions. Diagnostic and therapeutic approaches to the disease often go unrewarded, partly because of our incomplete understanding of the underlying immunopathogenesis.

OBJECTIVE

To characterize the immune response to the flea bite in patients with papular urticaria.

METHODS

This study included 45 randomly selected patients and 17 controls. Cutaneous allergy tests were performed. The histopathologic and immunohistochemical characteristics of cellular infiltrate in skin lesions were established. Immunoblot analysis was used to describe the specific characteristics of flea proteins recognized by IgE and IgG in patients' serum samples.

RESULTS

Cutaneous allergy test results were negative in 87% to 98% of patients and in 88% to 100% of controls. Histopathologic and immunohistochemical studies revealed a predominance of eosinophils and CD4+ T lymphocytes. Immunoblotting did not show significant differences in IgG response between patients and controls. IgE recognition of flea proteins appears to decrease as the disease progresses.

CONCLUSIONS

Our results suggest that the clinical manifestations of papular urticaria are mediated by a complex immune response involving more than one mechanism, with evidence forboth an IgE response and a cell-mediated type IV response.

The Prevention of Early Asthma in Kids study: design, rationale and methods for the Childhood Asthma Research and Education network

Pediatric asthma remains an important public health concern as its prevalence and cost to the health care system is rising. In order to promote innovative research in asthma therapies, the National Heart, Lung and Blood Institute created the Childhood Asthma Research and Education Network in 1999. As its first study, the steering committee of the Childhood Asthma Research and Education Network designed a randomized clinical trial to determine if persistent asthma could be prevented in children at a high risk to develop the disease. This communication presents the design of its first clinical trial, the Prevention of Asthma in Kids (PEAK) trial and the organization of the Childhood Asthma Research and Education Network that developed and implemented this trial. Studies of the natural history of asthma have shown that, in persistent asthma, the initial asthma-like symptoms and loss of lung function occur predominately during the first years of life. Therefore, in the Prevention of Asthma in Kids study, children 2 and 3 years old with a positive asthma predictive index were randomized to twice daily treatment with fluticasone 88 microg or placebo via metered-dose inhaler and Aerochamber for 2 years. The double blind treatment period was followed by a 1-year observational period. Lung function was measured by spirometry and oscillometry technique at 4-month intervals throughout the study. Bronchodilator reversibility and exhaled nitric oxide (ENO) studies were performed at the end of the treatment and observation periods. The primary outcome measure was the number of asthma-free days. Other secondary outcomes included number of exacerbations, use of asthma medications and lung function. These measures were chosen to reflect the progression of the disease from intermittent wheezing to persistent asthma and measurement of the extent of airflow limitation and airway reactivity.

Natural history of atopic dermatitis and its relationship to serum total immunoglobulin E in a population-based birth cohort study

We investigated the natural history of atopic dermatitis (AD) in a population-based birth cohort and assessed whether children at risk of visible eczema at 5 years of age can be identified from total immunoglobulin E (IgE) levels measured at 8, 12 and 18 months. AD data collected included a whole body examination for visible eczema at 49 months (4 years) and 61 months (5 years) of age and parent completed questionnaire data throughout their early lives. Children were divided into four groups based on their natural history of early AD: persistent (AD at 1, 6, 18, 30 and 42 months, n = 34), intermittent early onset (before 18 months of age, n = 495), intermittent late onset (18-42 months of age, n = 273) and unaffected (n = 429). Visible eczema at 5 years of age was present in 12.2% (117/957) (95% confidence interval [CI] 10.1-14.3%) of the children. Levels of total IgE at 8, 12 and 18 months of age were associated with early onset of AD, but not with AD of later onset. For all four natural history groups, the geometric mean total IgE at 12 months was higher in those who subsequently had visible eczema than those who did not. However, the degree of overlap was such that total IgE at 12 months of age was a poor predictor of eczema at age five. A cutoff point of 78 kU/l had the highest positive predictive value for visible eczema at 5 years of age of 28.6%, with a sensitivity of 12% and specificity of 95%.

Risk factors for asthma among children in Maputo (Mozambique)

BACKGROUND

Few studies have looked at risk factors for asthma in African children. We aimed to identify the risk factors associated with childhood asthma in Maputo (Mozambique).

METHODS

This case-control study included 199 age-matched children (100 asthmatic and 99 nonasthmatic) who attended Maputo Central Hospital between January 1999 and July 2000. We collected information concerning their familial history of atopy, birth weight, environment and breast-feeding. Detailed information about morbidity and treatment was obtained for each asthmatic child.

RESULTS

The children were aged between 18 months and 8 years; 60% were male. The asthmatic children were hospitalized more frequently than the nonasthmatic children (P < 0.0001). Most of the asthmatic children lived in the urban area of Maputo [odd ratio (OR) = 6.73, CI = 3.1-14.0, P < 0.0001], had a parental history of asthma (OR = 26.8, CI = 10.8-68.2, P < 0.0001) or rhinitis (OR = 4, CI = 1.2-13.3, P = 0.005), had at least parent who smoked and were weaned earlier than the nonasthmatic children (OR = 2.4, CI = 1.3-4.4, P < 0.001).

CONCLUSION

Childhood asthma was strongly associated with a family history of asthma and rhinitis, the place of residence, having smokers as parents and early weaning from maternal breast milk. These results highlight the need to reassess the management of asthmatic children in Maputo.

Can we prevent allergy?

Allergic conditions continue to increase steeply. The last two decades have seen many prevention trials, studying the effect of dietary and environmental interventions. These trials have yielded invaluable information about the atopic march and also highlighted the need for a clear and commonly used nomenclature as well as a need for better outcome measures. This review discusses primary and secondary prevention studies and their results.

Does environment mediate earlier onset of the persistent childhood asthma phenotype?

OBJECTIVE

We investigated the role of environmental and hereditary factors in determining whether persistent childhood wheezing phenotypes had an early or late onset.

METHODS

In a whole population birth cohort (n = 1456), children were seen at birth and at 1, 2, 4, and 10 years. At each visit, information was collected prospectively regarding wheeze prevalence and used to classify subjects into wheezing phenotypes. Information on genetic and environmental risk factors in early life was also obtained prospectively, and skin-prick testing to common allergens was performed at 4 years.

RESULTS

Early-onset persistent wheezers (n = 125) had wheeze onset in the first 4 years, still present at age 10, whereas late-onset persistent wheezers (n = 81) had wheeze onset after age 4 years that was still present at 10 years. Multivariate logistic regression analysis identified independent significance only for inherited factors (parental asthma, family history of rhinitis, eczema at 4 years, and atopic status at 4 years) in the development of late-onset persistent wheeze. However, low social class at birth, recurrent chest infections at 2 years, and parental smoking at 2 years plus inherited factors (eczema at 2 years; food allergy at 4 years; maternal asthma, sibling asthma, maternal urticaria, and atopic status at 4 years) demonstrated independent significance for early-onset persistent wheeze.

CONCLUSION

Inheritance seems to be of prime significance in the cause of persistent childhood wheeze. Environmental exposure in early life may combine with this tendency to produce an early onset of persistent wheeze. Absence of these environmental factors might delay but not prevent the onset of wheeze in children with atopic heredity.

Parental allergic status influences the risk of developing allergic sensitization and an asthmatic-like phenotype in canine offspring

Increasing evidence suggests that parental allergic status, especially that of the mother, may play a unique and important role in influencing the development of fetal infant immune responses to inhaled allergens, independently of genetic predisposition. We have developed an experimental model in dogs where the offspring from allergic parents, when exposed to inhaled allergen, develop allergic sensitization and an asthmatic phenotype, whereas the offspring from non-allergic parents do not. Offspring from ragweed-sensitized (two litters, n = 10) or non-sensitized (two litters, n = 11) Beagle dogs were exposed repeatedly, by inhalation, to ragweed or filtered air (negative control) beginning within 1 week after birth. Serum levels of total immunoglobulin (Ig)E, and ragweed-specific IgE and IgG, were measured at specific time-points up to 40 weeks after birth. Cell differentials in the bronchoalveolar lavage were determined on days 1 and 4 following ragweed instillation into the offspring's lungs at 26 weeks of age. Changes in pulmonary resistance following challenge with histamine and ragweed (five breaths) were measured at 40 weeks after birth. Offspring from sensitized parents exposed to ragweed developed elevated serum total IgE and ragweed-specific IgE and IgG, and showed an increased pulmonary resistance to histamine and ragweed, and increased numbers of eosinophils in bronchoalveolar lavage. In contrast, offspring from non-sensitized parents did not exhibit this immune response. These results suggest that parental allergic sensitivity is important in the development of allergic sensitization and an asthmatic phenotype in the offspring.

Ecological association of water hardness with prevalence of childhood atopic dermatitis in a Japanese urban area

The prevalence of symptoms of atopic eczema among Japanese children aged 6-7 years is the second highest in 56 countries. Reasons for such a high prevalence are unknown. This ecological study examined whether the positive association of water hardness with atopic dermatitis among British primary-school children also exists in Japan. Study subjects were 458,284 of 489,725 children, aged 6-12 years, in 1,016 public elementary schools in Osaka Prefecture with 44 municipalities. The study used data on water hardness and chlorine content of the water supply; prevalence of atopic dermatitis diagnosed by physicians and episodes of wheezing reported by the parents; and potential confounding factors by socioeconomic and health care status per municipality. The prevalence of atopic eczema was significantly higher in the highest water hardness category than that in the lowest (24.4% [n=2,288/9,362] and 22.9% [n=77,408/33,8267], respectively; adjusted odds ratio 1.12, 95% confidence interval 1.06-1.18; P<0.0001 for trend). A significant and slightly J-shaped relationship between chlorine content of the water supply and prevalence of atopic dermatitis was observed after adjustment for confounding factors. There were no apparent associations of water hardness and chlorine content of the water supply with prevalence of wheeze. Water hardness may increase the risk of atopic dermatitis among elementary-school children in Japan, as well as in the United Kingdom.

Effect of indoor environmental factors on development of atopic symptoms in children followed up to 4 years of age

The increased prevalence of atopic diseases reported in many Western countries is thought to be caused by changes in living conditions. For a long time attention was focused on indoor environmental factors and early feeding patterns, but during recent years other factors have received more attention. An unselected, Swedish, population-based cohort of 904 children were followed from the age of 3 months to 4 years. Questionnaires were sent to the mothers of the children when they were 3 months, 18 months and 4 years of age. A blood sample was taken from a subgroup of the children when they were 4 years old which was analysed for IgE specific antibodies to food and inhalant allergens. The prevalences of asthma, allergic eye-nose reactions, eczema, and food reactions at 4 years of age and a positive blood test were analysed as outcome factors. Features of housing and early feeding patterns were found to have limited effect on the development of allergies in the children. Presence of older siblings resulted in a decreased tendency to produce IgE antibodies. Early exposure to furry animals seemed to prevent the development of asthma. Children who were frequently infected up to 18 months of age showed an increased prevalence of allergic symptoms at 4 years of age. Children of mothers with a higher prevalence of complaints about indoor factors, or who had increased general symptoms or skin or mucous membrane symptoms ran a greater risk of developing various allergic symptoms. However, these children did not have higher levels of IgE antibodies. The reported allergic symptoms in the children may be due to non-immunological reactions, although it is also possible that the mothers may have over-reported such symptoms.

Breastfeeding and allergic disease: a multidisciplinary review of the literature (1966-2001) on the mode of early feeding in infancy and its impact on later atopic manifestations

BACKGROUND

Strategies to prevent children from developing allergy have been elaborated on the basis of state-of-the-art reviews of the scientific literature regarding pets and allergies, building dampness and health, and building ventilation and health. A similar multidisciplinary review of infant feeding mode in relation to allergy has not been published previously. Here, the objective is to review the scientific literature regarding the impact of early feeding (breast milk and/or cow's milk and/or formula) on development of atopic disease. The work was performed by a multidisciplinary group of Scandinavian researchers.

METHODS

The search in the literature identified 4323 articles that contained at least one of the exposure and health effect terms. A total of 4191 articles were excluded mainly because they did not contain information on both exposure and health effects. Consequently, 132 studies have been scrutinized by this review group.

RESULTS

Of the 132 studies selected, 56 were regarded as conclusive. Several factors contributed to the exclusions. The studies considered conclusive by the review group were categorized according to population and study design.

CONCLUSIONS

The review group concluded that breastfeeding seems to protect from the development of atopic disease. The effect appears even stronger in children with atopic heredity. If breast milk is unavailable or insufficient, extensively hydrolysed formulas are preferable to unhydrolysed or partially hydrolysed formulas in terms of the risk of some atopic manifestations.

Primary and secondary prevention of allergic airway disease

The incidence of atopic conditions is continuing to rise. The number of primary prevention cohorts is increasing and results are becoming available. There is a lack of true secondary prevention trials, however. This article reviews the results currently available from primary and secondary prevention studies.

Factors influencing symptom expression in children with bronchial hyperresponsiveness at 10 years of age

OBJECTIVES

We sought to identify factors associated with wheezing symptoms in children found to have bronchial hyperresponsiveness (BHR) at 10 years of age.

METHODS

Children were seen at birth, 1, 2, 4 and 10 years of age in an entire population birth cohort study (n = 1456). At each stage information was collected prospectively on genetic and environmental risk factors for BHR. Skin prick testing was performed at 4 and 10 years of age. Spirometry and methacholine bronchial challenge were conducted at 10 years of age when BHR was considered present if PC(20) FEV(1) was < 4.0 mg/mL. In children with BHR at 10 years of age, factors independently associated with current wheezing were determined by logistic regression.

RESULTS

BHR was identified in 169 10-year-olds at bronchial challenge, 55.6% of whom manifested current wheeze. In children with BHR, current wheezers had higher Log(10) total IgE and greater BHR than those who had never wheezed. Symptomatic BHR was independently associated with atopic sensitization (P <.001) and maternal asthma (P =.011) at 10 years of age. If only factors present in the first 4 years of life were considered, parental smoking at 4 years of age (P =.021), maternal asthma (P =.017), and atopic sensitization at 4 years of age (P =.004) were independently associated with symptomatic BHR at 10 years of age.

CONCLUSIONS

Symptomatic BHR is associated with greater degrees of BHR and higher total IgE. Heredity, atopy, and environmental exposure might influence symptom expression in children with BHR.

Breastfeeding, asthma, and atopic disease: an epidemiological review of the literature

Two main types of observational epidemiological studies have been used to question whether breastfeeding protects children from developing atopic disease and asthma. These are cohort studies of random samples of children and cohort studies of children with a family history of asthma or atopy. In each study type, exposure and outcome data are collected either prospectively or retrospectively. In this review, the primary objective was to assess the evidence of whether breastfeeding protects against asthma and atopic disease. As an outcome of this review, an analytical perspective with clinical implications is given.

Pet-keeping in childhood and adult asthma and hay fever: European community respiratory health survey

BACKGROUND

Whether pet-keeping early in life protects against or promotes allergy remains unclear.

OBJECTIVE

Our aim was to examine the effects of childhood pet-keeping on adult allergic disease in a large international population-based study, including information on sensitization, adult pet-keeping, and pet prevalence in the populations.

METHODS

We used information from structured interviews (n = 18,530) and specific IgE to common aeroallergens in blood samples (n = 13,932) from participants in the European Community Respiratory Health Survey (ECRHS) to analyze the associations between keeping pets and adult asthma and hay fever.

RESULTS

Keeping cats in childhood was associated with asthma only among atopic subjects, an association that varied between centers (P =.002) and was stronger where cats where less common (< 40% cats: odds ratio(wheeze) [OR(wheeze)] = 1.84, 95% CI = 1.31-2.57; 40%-60% cats: OR(wheeze) = 1.33, 95% CI = 1.10-1.61; > or =60% cats: OR(wheeze) = 0.98, 95% CI = 0.73-1.33). Dogs owned in childhood or adulthood were associated with asthma among nonatopic subjects (childhood: OR(wheeze) = 1.28, 95% CI = 1.13-1.46; adulthood: OR(wheeze) = 1.31, 95% CI = 1.14-1.51; both: OR(wheeze) = 1.69, 95% CI = 1.40-2.04). In atopic subjects, those who had owned dogs in childhood had less hay fever (OR = 0.85; 95% CI = 0.73-0.98) and no increased risk of asthma (OR(wheeze) = 1.01, 95% CI = 0.87-1.17). Respiratory symptoms were more common in subjects who had owned birds during childhood (OR(wheeze) = 1.12; 95% CI = 1.02-1.23) independent of sensitization.

CONCLUSIONS

The effects of pet-keeping in childhood varied according to the type of pet, the allergic sensitization of the individual, and the wider environmental exposure to allergen. Cats owned in childhood were associated with more asthma in sensitized adults who grew up in areas with a low community prevalence of cats. Dogs owned in childhood seemed to protect against adult allergic disease but promote nonallergic asthma.

Treating the wheezing infant

The management of infants and small children with asthma is a challenging task because of the many issues unique to this age group that deserve special consideration. The diagnosis of asthma is limited by inherent difficulties in obtaining objective measures of lung function and airway inflammation. In persistently symptomatic patients, the decision to initiate controller therapy is not as great an issue as it is in infants and young children with recurrent episodic wheeze in whom early intervention may allow a window of opportunity potentially to alter the course of the disease. The reality is that even if atopy has been consistently implicated in the development of persistent asthma, there is not a well-established set of criteria by which patients who are likely to benefit from early intervention controller therapy can be identified. Hence, large prospective studies need to be performed evaluating the impact of early pharmacologic intervention on the natural history of infantile asthma. Many areas needing investigation involve what medications to use, how best to deliver the medications, and how to monitor the response to treatment. Only a few medications have been approved for use in this population. Long-term studies evaluating available drugs such as inhaled glucocorticoids, LABAs, and the leukotriene-modifying agents in young children still need to be performed.

Therapeutic modalities for cow's milk allergy

OBJECTIVE

To discuss current therapeutic modalities for cow's milk allergy and its prevention.

DATA SOURCES AND STUDY SELECTION

The sources of data include original clinical studies carried out at Ste. Justine Hospital, as well as a systematic search of the published English and French language scientific literature restricted to human subjects using computerized searches (National Public Library of Medicine, Cochrane Database Systems Review) from 1997 to 2002. Search terms for article retrieval included food allergy, milk allergy, therapy, and prevention.

CONCLUSIONS

The therapy of food allergies depends upon an accurate diagnosis, which remains a challenge in non--IgE-mediated cases. Dietary exclusion remains the mainstay of therapy, with medications reserved for exceptional patients. Preliminary evidence suggests that pancreatic enzyme supplementation may be of benefit for cases with multiple food allergies and severe eczema. Hydrolysate formula use is currently recommended for dietary allergy prevention in infants at an increased risk when maternal milk is insufficient or unavailable. The use of partially hydrolyzed formulas to prevent allergic disorders, including atopic dermatitis, is supported by clinical studies, but cannot be used in the already sensitized, milk-allergic child. Probiotics show enormous potential in preventing food allergic disorders as well.

Early sensitisation and development of allergic airway disease - risk factors and predictors

The development and phenotypic expression of allergic airway disease depends on a complex interaction between genetic and several environmental factors, such as exposure to food, inhalant allergens and non-specific adjuvant factors (e.g. tobacco smoke, air pollution and infections). The first months of life seem to be a particularly vulnerable period and there is evidence that sensitisation is related to the level of allergen exposure during early life. At present, the combination of atopic heredity and elevated cord-blood IgE seems to result in the best predictive discrimination as regards development of allergic disease at birth. Early sensitisation, cow's milk allergy and atopic eczema are predictors for later development of allergic airway disease. Exposure to indoor allergens, especially house dust mite allergens, is a risk factor for sensitisation and development of asthma later in childhood in high-risk infants and infants with early atopic manifestations.

The prevalence, characteristics of and early life risk factors for eczema in 10-year-old children

Eczema is a common infantile disease but its nature and extent during later childhood remains unclear. In a whole-population birth cohort study (n = 1456) we examined prevalence and characteristics of eczema amongst 10-year-old children. At this age 1373 (94%) children completed ISAAC questionnaires, 1043 (72%) skin prick testing and 953 (65%) serum inhalant IgE antibody screening. At 10 years of age prevalence of eczema ever was 41.0% and for current eczema was 13.7% (combined current itchy rash and eczema ever). Most current eczema (71.0%) began before 4 years of age, but was associated with low morbidity at 10 years. Amongst children with diagnosed eczema at 4 years of age, 56.3% had current eczema at 10 years. Atopy (positive skin test) and other allergic states were associated with current eczema (p < 0.001). Risk factor analysis for current eczema identified independent significance for atopy (p = 0.01), rhinitis (p = 0.04) and food allergy (p = 0.01) at 4 years, plus maternal asthma (p = 0.03). Diagnosed rhinitis at 4 years emerged as a significant predictor of persistent disease. Eczema is not simply a transient infantile condition but a common problem at 10 years of age, often reflecting persistent disease from early childhood. Inherited predisposition towards atopy is the predominant risk factor for this state.

Early endotoxin exposure and atopy development in infants: results of a birth cohort study

BACKGROUND

Exposure to endotoxin in childhood is currently discussed to protect from the development of allergic diseases.

OBJECTIVE

To study the effect of early endotoxin exposure on incidence of atopic sensitization, atopic dermatitis and wheezing until the age of 2 years in infants with different risk status in terms of parental atopy.

METHODS

Data of 1942 infants of an ongoing birth cohort study were analysed by logistic regression. Endotoxin was measured in settled dust of the mothers' mattresses at infants' age of 3 months. Data on allergic symptoms and physicians' diagnoses were gathered by questionnaire. Sensitization to common food and inhalant allergens was assessed by specific serum IgE.

RESULTS

High endotoxin levels increased the risk of repeated wheeze [adjusted odds ratio (OR) for 4th exposure quartile (Q4) 1.52, 95% confidence interval (CI) 1.08-2.14], but were associated with neither sensitization to food allergens nor atopic dermatitis. Stratification by parental atopy showed that there was an association of endotoxin exposure with incidence of repeated wheeze as well as with sensitization to inhalant allergens (P for trend = 0.008 and 0.044, respectively) only in infants with parental atopy, with the highest risk in the 4th exposure quartile (repeated wheeze: ORQ4 1.77, 95% CI 1.14-2.73; sensitization to inhalant allergens: ORQ4 1.69, 95% CI 0.70-4.11).

CONCLUSION

Early endotoxin exposure in terms of mattress dust endotoxin levels seemed to increase the risk of atopic reactions to inhalant allergens at the age of 2 years, especially in infants at risk due to parental atopy. Our data disagree with an early protective effect of endotoxin on atopy development until the age of 2 years.

A dual long-term effect of breastfeeding on atopy in relation to heredity in children at 4 years of age

BACKGROUND

The long-term effect of early feeding on atopic sensitization is still unsolved. The aim of this study was to evaluate the long-term effect of breastfeeding on atopy in groups of 4-year-old children stratified by atopic heredity.

METHODS

We collected four groups of 4-year-old children from a birth cohort: two groups with differing backgrounds of atopic heredity, all exclusively breast-fed for at least 3 months; and two groups with differing atopic heredity, but all fed with cow's milk-based formula during their first weeks. The data were collected with a questionnaire, skin prick testing, and measurement of serum total and allergen-specific IgE levels.

RESULTS

Breastfeeding significantly decreased the risk of allergic rhino-conjunctivitis [odds ratio (OR) 0.41, 95% confidence interval (CI) 0.18-0.95] and sensitization to furred pets, as measured by skin prick results, in children with atopic heredity, whereas in children without atopic heredity, breastfeeding was related to an increased risk of symptomatic atopy (OR 2.57, 95% CI 1.16-5.70), and high serum IgE values. A significant interaction was found between heredity and breastfeeding.

CONCLUSIONS

The long-term effect of breastfeeding was dual: in children with atopic heredity, breastfeeding protected against atopy, whereas in children without atopic heredity, it increased the risk of atopy.

Developmental immunology: clinical application to allergy-immunology

BACKGROUND

An increase in prevalence of allergic diseases has been seen at an unprecedented rate in many countries throughout the world. Associated with this increase in allergic disease has been a disturbing increase in morbidity and mortality of such diseases as asthma despite the availability of several new therapeutic agents over the past 2 to 3 decades. The search for both environmental factors, eg, new allergens, as well as biologic markers of genetic susceptibility, eg, respiratory viruses, has yielded considerable promise for an explanation for this rising prevalence of allergic disease.

OBJECTIVE

To present a central unifying hypothesis based upon recent knowledge concerning the developing human immune system and its interaction with external environmental factors, particularly viral infections, as a basis for a clearer understanding of the changing faces of the allergic diseases throughout the lifespan of the individual.

DATA SOURCES

English language articles were selected from PubMed, as well as selected abstracts that would have immediate, practical clinical implications.

RESULTS

Review of the current literature strongly suggests a relationship between delayed acquisition of Th1 function in the allergy-prone infant, not only as a predictive marker of susceptibility to the development of allergic disease but also as an explanation for the unique vulnerability of these infants to viral infection, eg, bronchiolitis. Furthermore, viral infection during early development in the allergy-prone infant appears to facilitate allergic sensitization in early infancy. This interesting triad of immune deficiency, viral infection, and atopic genetic susceptibility may provide a basis for early detection of allergic disease and may offer new intervention strategies for the prevention of allergic and infectious disease in the young infant.

Rhinitis in 10-year-old children and early life risk factors for its development

AIM

To study the prevalence, characteristics of and risk factors for childhood rhinitis.

METHODS

In a whole population birth cohort study (n = 1,456) the prevalence and characteristics of rhinitis among 10-y-old children were examined. At this age 1373 children (94%) completed standardized questionnaires, 1,043 (72%) skin-prick testing, 953 (65%) serum inhalant immunoglobulin E antibody screening and 784 (54%) methacholine bronchial challenges.

RESULTS

At the age of 10 y the prevalence of hayfever ever was 18.6% and current nasal symptoms (rhinitis) 22.6%. Rhinitis at 10 y was largely seasonal and associated with low morbidity, although 62.7% of cases required pharmacological treatment. Atopy (positive skin test) and other allergic states were associated with rhinitis (p < 0.001). Wheeze or diagnosed asthma was higher with coexistent rhinitis. Among wheezing children physician-diagnosed asthma (p < 0.024) and inhaled corticosteroid use (p < 0.001) were greater with the presence of rhinitis. Significant bronchial hyperresponsiveness (methacholine concentration giving a 20% fall in forced expiratory volume in I s <4.0 mg ml(-1)) was greater if rhinitis was present even when the child did not wheeze (p < 0.001). Risk factor analysis for rhinitis identified the independent significance for atopy (p < 0.001) and eczema (p = 0.009) at the age of 4 y plus paternal rhinitis (p < 0.001), maternal rhinitis (p = 0.033) and maternal food allergy (p = 0.016).

CONCLUSION

Rhinitis is common at the age of 10 y, with strong associations with atopy, wheezing, asthma and bronchial hyperresponsiveness. An inherited predisposition towards atopy appears to predominate over environment in the aetiology of this state.

Characterization of wheezing phenotypes in the first 10 years of life

BACKGROUND

Childhood wheezing illnesses are characterized into different phenotypes. However, severity of the disease associated with these phenotypes has not been extensively studied.

OBJECTIVES

To determine characteristics of childhood wheezing phenotypes in the first decade of life using health outcomes plus measurements of atopy, lung function and bronchial hyper-responsiveness.

METHODS

A whole population birth cohort (n = 1456) was prospectively studied to examine the natural history of childhood wheezing. Children were seen at 1, 2, 4 and 10 years for questionnaire completion and prospectively collected data used to define wheezing phenotypes. Assessment was made of adverse health outcomes plus spirometry, bronchial hyper-responsiveness, serum IgE measurement at 10 years and skin test sensitization at both 4 and 10 years for wheezing phenotypes.

RESULTS

Phenotypic analysis identified that 37% early life wheezers (symptom onset by age 4 years) still wheezed at 10 years. These persistent wheezers showed significantly more physician-diagnosed asthma in early life (P < 0.005 at 2 years) than early transient wheezers (wheezing transiently with onset by age 4 years). Overall they experienced greater multiple hospital admissions (P = 0.024), specialist referral (P = 0.009) and use of inhaled (P < 0.001) and oral steroids (P < 0.001) than early transient wheezers. They also demonstrated enhanced bronchial hyper-responsiveness compared with early transient wheezers (P < 0.001). However, both groups of early life wheezers showed impairment of baseline lung function at 10 years in comparison with non-wheezers: FEV1 (P < 0.029) and FEV1/FVC ratio (P < 0.001) with persistent wheeze and PEF (P = 0.036) with early transient wheeze. Late-onset wheezers (onset from 5 years onwards) had similar BHR to persistent wheezers but maintained normal lung function at age 10 and had lower cumulative prevalence of adverse health outcomes than persistent wheezers.

CONCLUSIONS

Persistent wheezing with early childhood onset is associated with substantial morbidity in the first decade of life in association with high levels of atopy, bronchial hyper-responsiveness and impaired lung function at 10 years of age. Late-onset wheezing in the first decade of life could harbour potential for similarly significant disease subsequently.

The epidemiology of atopic dermatitis in Italian schoolchildren

BACKGROUND

Atopic dermatitis (AD) is common in children in industrialized countries. Only one large population study on its prevalence has been conducted in Italy, based on self-report questionnaire. The present study was designed to estimate the prevalence of AD in schoolchildren in Italy by dermatologists' assessment and by UK Working Party criteria, and to investigate associated symptoms and factors.

METHODS

Cross-sectional survey on a random sample of 9-year-old schoolchildren from seven Italian cities. Children were examined by experienced dermatologists. Parents and teachers answered standardized questionnaires.

RESULTS

Of the 1369 children examined, 88 had a diagnosis of AD, with an estimated point prevalence of 5.8% (95% CI 4.5-7.1) in the reference population. The reported lifetime prevalence was 15.2 (95% CI 12.2-18.2) for AD, 11.9% (95% CI 9.0-14.8) for asthma, and 17.6% (95% CI 14.6-20.7) for rhino-conjunctivitis. The strongest associated factor was the presence of AD in at least one parent. No association of AD with maternal smoking during pregnancy, birth weight, maternal age at the time of the child birth and breast-feeding was observed. The environmental characteristics of the house and the school did not correlate with the prevalence of AD. Episodes of lower respiratory tract infections were associated with asthma, and to a lower extent also with AD and rhinitis.

CONCLUSIONS

The prevalence of doctor-diagnosed AD in Italian schoolchildren is comparable to those reported for other developed countries. Family history of atopy was the single most important associated factor, while the complex interplay of environmental factors remains to be elucidated.

Animal models in food allergy: assessment of allergenicity and preventive activity of infant formulas

Food allergies occur in about 5-10% of the overall infant and small-child population. Cow's milk protein allergy (CMPA) is the most common in young infants, with a 2-4% incidence. When breastfeeding is not possible, hypoallergenic (HA) cow's milk based formulas are usually given during the first months of life for prevention of CMPA. Depending on primary (sensitization) or secondary (triggering) prevention, the requested quality of HA formulas may be different. Besides in vitro methods, in vivo and ex vivo animal models are helpful in assessing residual allergenicity and the preventive effect of HA formulas. The sensitizing capacity of a formula can be examined by either the parenteral rat (IgE), the guinea pig (IgG1a mediated) or the oral mouse (IgE) models. The triggering IgE mediated allergenicity is tested by a parenteral rat model with oral gavage for intestinal mast cell protease (RMCPII) release. These animal models are also used for testing the oral tolerance inducing capacities of formulas. Together with cellular in vitro assays, animal models are very helpful in predicting allergenicity and the tolerogenic potential of HA infant formulas.

Indoor allergen exposure in the development of allergy and asthma

Research evidence supports a causative relationship between indoor allergen exposure and the development of asthma. Epidemiologic studies demonstrate that exposure to indoor allergens, particularly house-dust mites and cockroaches and, to a lesser extent, animal allergens and mold, is a risk factor for the development of sensitization and perhaps respiratory symptoms. Sensitization to indoor allergen is clearly a major risk factor for the development of asthma and allergy. There is also epidemiologic and experimental evidence that, in sensitized subjects, higher exposure to indoor allergen causes morbidity. Most, but not all, prospective studies support the causative link between allergen exposure and asthma. Additional evidence comes from the prevention studies, in which reduction in indoor allergen exposure may lead to improvement in symptoms, pulmonary function, and bronchial hyperresponsiveness, and, if practiced, in early years of life, perhaps the development of asthma and allergy.

Breastfeeding and the prevalence of symptoms of allergic disorders in Japanese adolescents

BACKGROUND

Environmental factors acting early in life are key determinants of the incidence of allergic disease. Whether breastfeeding is protective against allergic disorders remains controversial.

OBJECTIVE

The present cross-sectional study examined the relationship between feeding patterns in the first 3 months of life and the prevalence of symptoms of wheeze, atopic eczema, and rhinoconjunctivitis during the past 12 months in Japanese adolescents.

METHODS

The subjects were 5614 of 9008 students (62%) aged 12-15 years from all public junior high schools in Suita, Japan in 2001. This study used the diagnostic criteria of the International Study of Asthma and Allergies in Childhood. Adjustment was made for gender, grade, number of older siblings, and parental history of allergy.

RESULTS

Feeding pattern was unrelated to the prevalence of wheeze or rhinoconjunctivitis. The prevalence of atopic eczema was significantly higher in children who had been breastfed than in artificial milk feeders (adjusted odds ratios = 1.40 and 1.56, 95% confidence intervals: 1.01-1.98 and 1.13-2.22 for mixed milk intake and breastfeeding only vs. artificial milk consumption, respectively; P = 0.01 for linear trend). When children were divided according to a positive or negative allergic history in at least one parent, an increased prevalence of atopic eczema associated with breastfeeding was found in children with a negative parental allergic history compared with those with a positive parental allergic history.

CONCLUSION

The findings suggest that breastfeeding may be associated with an increased prevalence of atopic eczema, especially among children without a parental history of allergy.

Pets in the home and the development of pet allergy in adulthood. The Copenhagen Allergy Study

BACKGROUND

The aim of the study was to investigate the association between exposure to cat and dog in the home and the development (incidence) of IgE sensitization to cat and dog.

METHODS

Participants in a population-based study of 15-69-year-olds in 1990 were invited to a follow-up in 1998. Serum IgE antibodies against common inhalant allergens was assessed in 734 subjects (participation rate 69.0%) on two occasions 8 years apart. Information about current or previous keeping of cats and dogs in the home was obtained in a questionnaire at baseline.

RESULTS

A cat in the home currently was significantly associated with the development of IgE sentisization to cat (adjusted odds ratio 8.4, 95% confidence interval (CI) 1.7-42.7). Moreover, an atopic predisposition in terms of IgE sensitization to allergens other than cat at baseline was an independent risk factor for the development of IgE sensitization to cat. A dog in the home was not significantly associated with the development of IgE sensitization to dog.

CONCLUSIONS

In this adult population, exposure to a cat in the home increased the risk of developing IgE sensitization to cat. More prospective data are needed on this issue.

Exposure to pets and atopic dermatitis during the first two years of life. A cohort study

The aim of this study was to assess the association between keeping pets in early childhood and the occurrence of atopic dermatitis in an ongoing birth cohort followed up to the age of 2 years. We analyzed data of 4578 children in the intervention and observation part of an ongoing cohort study. The children were recruited at birth in the two study regions Wesel and Munich between January 1996 and June 1998. Information on atopic diseases and pet ownership was obtained by questionnaire at the child's first and second birthday. The logistic regression model showed a negative association between 'keeping any pet' and in particular 'keeping dogs' in the 1st year of life and the development of atopic dermatitis in the 1st and the 2nd years of life. The protective effects remained statistically significant after adjusting for several possible confounding variables (1st year(any) pet OR 0.71, 95% CI [0.55;0.92], 1st year(dog) OR 0.62, 95% CI [0.39;0.98], 2nd year(any) pet OR 0.74, 95% CI [0.57;0.97], 2nd year(dog) OR 0.63, 95% CI [0.40;0.98]). Ownership of small furred pets (hamster, rabbit and guinea pig) also showed a borderline protective effect for the 1st year. We assume an association between keeping pets and undefined environmental factor(s) that contribute protectively to the development of atopic dermatitis in early life, presumably by effects on the maturation of the immune system.

Breast feeding and allergic diseases in infants-a prospective birth cohort study

AIMS

To investigate the effect of breast feeding on allergic disease in infants up to 2 years of age.

METHODS

A birth cohort of 4089 infants was followed prospectively in Stockholm, Sweden. Information about various exposures was obtained by parental questionnaires when the infants were 2 months old, and about allergic symptoms and feeding at 1 and 2 years of age. Duration of exclusive and partial breast feeding was assessed separately. Symptom related definitions of various allergic diseases were used. Odds ratios (OR) and 95% confidence intervals (CI) were estimated in a multiple logistic regression model. Adjustments were made for potential confounders.

RESULTS

Children exclusively breast fed during four months or more exhibited less asthma (7.7% v 12%, OR(adj) = 0.7, 95% CI 0.5 to 0.8), less atopic dermatitis (24% v 27%, OR(adj) = 0.8, 95% CI 0.7 to 1.0), and less suspected allergic rhinitis (6.5% v 9%, OR(adj) = 0.7, 95% CI 0.5 to 1.0) by 2 years of age. There was a significant risk reduction for asthma related to partial breast feeding during six months or more (OR(adj) = 0.7, 95% CI 0.5 to 0.9). Three or more of five possible allergic disorders-asthma, suspected allergic rhinitis, atopic dermatitis, food allergy related symptoms, and suspected allergic respiratory symptoms after exposure to pets or pollen-were found in 6.5% of the children. Exclusive breast feeding prevented children from having multiple allergic disease (OR(adj) = 0.7, 95% CI 0.5 to 0.9) during the first two years of life.

CONCLUSION

Exclusive breast feeding seems to have a preventive effect on the early development of allergic disease-that is, asthma, atopic dermatitis, and suspected allergic rhinitis, up to 2 years of age. This protective effect was also evident for multiple allergic disease.

Rhinitis (allergic and nonallergic) in an atopic pediatric referral population in the grasslands of inland South Africa

BACKGROUND

Allergic rhinitis is a common condition, which causes considerable morbidity. South African data are scarce.

OBJECTIVE

We sought to describe allergic rhinitis in atopic children in inland South Africa.

METHODS

An observational, descriptive study of rhinitis occurring in 771 new patients seen consecutively by a single observer at a referral pediatric allergy clinic (Universitas Hospital, Bloemfontein) over an 8 1/2-year period (August 1984 to March 1993) was carried out. A detailed questionnaire was used to record clinical data. Chest and sinus x-rays, skin prick testing, and radioallergosorbent test were performed, and serum immunoglobulin E levels were determined. Response to drug treatment regimens was recorded at subsequent followup visits.

RESULTS

Significant rhinitis was reported in 78.1% of patients, and mild intermittent rhinitis was reported in 21.4%. Male to female ratio was 1.6:1. Median age at onset of rhinitis symptoms was 6 months (range 0 months to 12 years), with 30.1% experiencing symptoms from birth. Rhinitis was chronic in 61.3%, although 53.5% reported seasonal variation. More children with rhinitis were born in midsummer than during other seasons, although this did not reach statistical significance (P = 0.46). Breast-feeding had no protective effect, and parental smoking and household pets were not found to be risk factors. Family history was positive for allergic rhinitis in 88% of patients. Exposure to dust, weather changes, strong odors, pets, pollens, and tobacco smoke were the most common trigger factors. Sinus x-ray findings associated poorly with clinical findings. The most common allergens identified were grass pollen, tree pollen, and cat. Oral antihistamines provided good symptomatic relief in 62.9% of patients who used them. Intranasal corticosteroids provided good relief in 78.0% of those who used them, and ketotifen provided relief in 54.4% of those who used it.

CONCLUSIONS

Rhinitis is a common manifestation of allergy in the population studied. Onset occurs early in childhood. A family history of allergy is a risk factor for the development of the condition, and grass pollen is the most common allergen involved. Special investigations are of limited value. Appropriate treatment is very effective.

Differences in the prevalence of asthma and current wheeze between Jews and Arabs: results from a national survey of schoolchildren in Israel

BACKGROUND

There is evidence that the prevalence of asthma is higher in Jewish schoolchildren than in Arab schoolchildren. It is not clear to what extent other risk factors explain these differences.

OBJECTIVE

To evaluate whether the population group differences in the prevalence of asthma and current wheeze remain after adjustment for several potential risk factors.

METHODS

A national survey of 10,057 13- to 14-year-old schoolchildren was carried out in Israel in 1997. There were 7,436 Jewish children and 2,621 Arab children. Differences in the two population groups were examined while controlling for demographic and environmental factors such as: sex, parental education, parental smoking and asthma, crowding, and presence of older siblings.

RESULTS

The prevalence of asthma and current wheeze was significantly higher in Jewish children compared with Arab children. The asthma prevalence was 7.8% for Jewish children and 4.9% for Arab children (P = 0.001), and prevalence of current wheeze was 20.7 and 10.1%, respectively (P = 0.001). After adjustment for demographic and environmental factors, the prevalence of asthma and current wheeze was still increased in the Jewish population (odds ratios: 1.51; 95% confidence interval [CI] = 1.06 to 2.15; 2.15 95% CI = 1.70 to 2.73, respectively). History of asthma in parents and residence in a rural area were significant risk factors for asthma and current wheeze. In addition, the presence of less than three older siblings was a significant risk factor for asthma, and female sex, ever having pets, and maternal smoking were significantly associated with current wheeze.

CONCLUSIONS

The differences between Jewish and Arab children were not explained by the studied factors. Genetic factors, different environmental exposure, and nutritional habits should be studied to further explain the differences between these populations.

House dust endotoxin and allergic sensitization in children

A higher exposure to endotoxin was hypothesized to contribute to lower prevalence of allergic sensitization and hay fever in children growing up on a farm. We studied the association between house dust endotoxin and allergic sensitization. We randomly selected 740 children, aged between 5 and 10 years, from a group of children who participated in two cross-sectional surveys performed in Saxony-Anhalt, Germany, from 1992 to 1993 and from 1995 to 1996, such that 50% of the children were atopic or had a diagnosis of asthma. From 1996 to 1998, we collected living-room floor dust in the homes of 454 of these children (61%). The content of endotoxin in house dust was quantified using a chromogenic kinetic limulus amoebocyte lysate test and was related with health outcomes measured in the preceding cross-sectional surveys. Multiple logistic regression analyses adjusted for place of residence, sex, age, parental education, parental atopy, and pet ownership showed a negative association between exposure to endotoxin and sensitization to one or more allergens (aOR [95% CI] 0.95 [0.83; 1.10]) and two or more allergens (aOR [95% CI] 0.80 [0.67; 0.97]) using 0.35 kU/L as the cutoff value for sensitization. The protective effect was strengthened with increasing degree of sensitization. In conclusion, exposure to higher levels of house dust endotoxin is associated with lower prevalence of allergic sensitization in children.

Skin-prick test findings in atopic asthmatic children: a follow-up study from childhood to puberty

In a prospective cohort study we investigated the course of allergic sensitization from childhood to puberty in a group of children with atopic asthma. An attempt was made to correlate the findings with the persistence of asthma. A total of 150 children with atopic asthma established at 7 years of age were evaluated when 8-10 years of age. A battery of skin-prick tests (SPTs) to common environmental allergens, a detailed clinical history for asthma severity classification, and spirometric analyses, were performed. In 127 of these children a re-evaluation was performed at puberty. A variety of statistical methods were used to analyze the results regarding changes in skin test reactivity to individual aeroallergens and atopic index (degree of atopy), as well as to determine any correlation between these changes and the persistence of asthma in puberty. A wide spectrum of modification in skin reactivity to common environmental allergens was observed, including the complete loss of sensitization to some allergens or the development of a new one to others. Specifically, 34% of asthmatic children sensitive to Dermatophagoides pteronyssinus and 52.7% sensitive to cat lost their sensitivity in puberty, while only 7.5% and 11.1%, respectively, became sensitized (p = 0.03 and p = 0.001, respectively). In contrast, regarding pollen sensitivity, 30.2% and 24% of asthmatic children became sensitive in puberty to olive pollen and grasses mix, respectively, and only 11.7% and 12.5%, respectively, lost their sensitivity to these allergens (p = 0.04). No correlation was shown between the skin test reactivity changes to individual allergens and the persistence of asthma, but a significant correlation was found between atopic index to indoor allergens in childhood and the persistence of asthma at puberty (p = 0.04). Interestingly, multi-sensitivity to allergens (>/= 4 allergens) in childhood was also found to correlate with the persistence of asthma at puberty [p = 0.05, odds ratio (OR) = 2.65, 95% confidence interval (CI) 1.2-7.2]. Our findings indicate that significant modification of skin reactivity to common environmental allergens in atopic children with asthma in puberty can occur. However, no association between these changes and the persistence of asthma could be demonstrated, although children with indoor allergic sensitization and multi-reactivity were found to have a higher probability of maintaining their asthma in puberty.

How should a birth cohort study be organised? Experience from the German MAS cohort study

Birth cohort studies offer the opportunity to study average risks, rates and occurrence times of disease longitudinally from birth. The effect of genetic and environmental factors and their interactions can be studied. Furthermore, quantity and duration of exposure to environmental agents can be evaluated prospectively. However, prospective birth cohort studies are expensive, labour intensive and take many years to complete. Loss of subjects over time as well as recall bias complicate the interpretation of observations. This paper summarises the potential pitfalls of such studies and discusses the experience of the German Multicentre Allergy Study (MAS), which began in 1990 in five German cities and included 1314 newborns for the study of the natural course of atopic diseases.