The development of allergy in high-risk children

Risk Factors for Wheezing in Primary School Children in Bursa, Turkey

Background

Wheezing is the most common symptom of childhood respiratory tract illnesses. It is important not only for its associated acute morbidity, but also for the fact that early childhood wheezing confers a high risk for asthma. Epidemiological studies from various countries show that 10–15% of children <1 year of age and 25% of children <5 years of age have wheezing-associated respiratory tract illness, and one-third of these children develop asthma later in life.

Methods

In this retrospective study, we evaluated the association between a history of wheezing and prenatal, postnatal, familial, and environmental risk factors in 858 7-year-old children, randomly selected from seven primary schools in Bursa, Turkey, by means of an easy-to-understand questionnaire form. Among these children, 12.4% had a history of early transient wheezing, 7.1% had persistent wheezing, and 7.7% had late onset wheezing; 72.8% had no wheezing symptoms and 33.3% of children who experienced wheezing during the first 3 years of life had physician-diagnosed asthma.

Results

Notable risk factors associated with wheezing were as follows: male gender, lower socioeconomic status, premature birth, maternal smoking during pregnancy, bottle-feeding before 2 months of age, dampness and mold at home, hospitalization due to any respiratory illness in infancy, history of croup between 6 months and 5 years of age, frequent upper respiratory infections during the first 3 years of life, allergic eczema in the child, and any allergic disease in the mother or siblings.

Conclusion

This study shows that the high rates of reported wheezing in the 858 primary school children in Bursa are clearly attributable to important risk factors that have long been recognized and discussed by researchers worldwide, and this suggests that all efforts at primary prevention may be insufficient.

Is there a march from early food sensitization to later childhood allergic airway disease? Results from two prospective birth cohort studies

BACKGROUND

The march from early aeroallergen sensitization to subsequent respiratory allergy is well established, but it is unclear whether early life food sensitization precedes and further increases risk of allergic airway disease.

OBJECTIVE

To assess the association between food sensitization in the first 2 years of life and subsequent asthma and allergic rhinitis by age 10-12 years.

METHODS

We used data from two independent cohorts: the high-risk Melbourne Atopic Cohort Study (MACS) (n = 620) and the population-based LISAplus (n = 3094). Food sensitization was assessed at 6, 12, and 24 months in MACS and 24 months in LISAplus. Multiple logistic regressions were used to estimate associations between sensitization to food only, aeroallergen only, or both and allergic airway disease.

RESULTS

When compared to non-sensitized children, sensitization to food only at 12 months in MACS and 24 months in LISAplus was associated with increased risk of current asthma (aOR = 2.2; 95% CI 1.1, 4.6 in MACS and aOR = 4.9; 2.4, 10.1 in LISAplus). Similar results were seen for allergic rhinitis. Additionally, cosensitization to food and aeroallergen in both cohorts at any tested point was a stronger predictor of asthma (at 24 months, aOR = 8.3; 3.7, 18.8 in MACS and aOR = 14.4; 5.0, 41.6 in LISAplus) and allergic rhinitis (at 24 months, aOR = 3.9; 1.9, 8.1 in MACS and aOR = 7.6; 3.0, 19.6 in LISAplus).

CONCLUSIONS

In both cohorts, food sensitization (with or without aeroallergen sensitization) in the first two years of life increased the risk of subsequent asthma and allergic rhinitis. These findings support the role of early life food sensitization in the atopic march and suggest trials to prevent early onset have the potential to reduce the development of allergic airways disease.

The march from early life food sensitization to allergic disease: a systematic review and meta-analyses of birth cohort studies

BACKGROUND

There is growing evidence for an increase in food allergies. The question of whether early life food sensitization, a primary step in food allergies, leads to other allergic disease is a controversial but important issue. Birth cohorts are an ideal design to answer this question.

OBJECTIVES

We aimed to systematically investigate and meta-analyse the evidence for associations between early food sensitization and allergic disease in birth cohorts.

METHODS

MEDLINE and SCOPUS databases were searched for birth cohorts that have investigated the association between food sensitization in the first 2 years and subsequent wheeze/asthma, eczema and/or allergic rhinitis. We performed meta-analyses using random-effects models to obtain pooled estimates, stratified by age group.

RESULTS

The search yielded fifteen original articles representing thirteen cohorts. Early life food sensitization was associated with an increased risk of infantile eczema, childhood wheeze/asthma, eczema and allergic rhinitis and young adult asthma. Meta-analyses demonstrated that early life food sensitization is related to an increased risk of wheeze/asthma (pooled OR 2.9; 95% CI 2.0-4.0), eczema (pooled OR 2.7; 95% CI 1.7-4.4) and allergic rhinitis (pooled OR 3.1; 95% CI 1.9-4.9) from 4 to 8 years.

CONCLUSION

Food sensitization in the first 2 years of life can identify children at high risk of subsequent allergic disease who may benefit from early life preventive strategies. However, due to potential residual confounding in the majority of studies combined with lack of follow-up into adolescence and adulthood, further research is needed.

The natural history of IgE-mediated food allergy: can skin prick tests and serum-specific IgE predict the resolution of food allergy?

IgE-mediated food allergy is a transient condition for some children, however there are few indices to predict when and in whom food allergy will resolve. Skin prick test (SPT) and serum-specific IgE levels (sIgE) are usually monitored in the management of food allergy and are used to predict the development of tolerance or persistence of food allergy. The aim of this article is to review the published literature that investigated the predictive value of SPT and sIgE in development of tolerance in children with a previous diagnosis of peanut, egg and milk allergy. A systematic search identified twenty-six studies, of which most reported SPT or sIgE thresholds which predicted persistent or resolved allergy. However, results were inconsistent between studies. Previous research was hampered by several limitations including the absence of gold standard test to diagnose food allergy or tolerance, biased samples in retrospective audits and lack of systematic protocols for triggering re-challenges. There is a need for population-based, prospective studies that use the gold standard oral food challenge (OFC) to diagnose food allergy at baseline and follow-up to develop SPT and sIgE thresholds that predict the course of food allergy.

Skin prick test to foods in childhood atopic eczema: pros and cons

Skin prick tests are the first investigation in allergy diagnostics and their use is described in all the guidelines on atopic eczema. However, the clinical usefulness of skin prick tests is the subject of great debate. On the one hand, skin prick tests allow the identification both of individuals at risk for food allergy and of the allergen inducing the eczematous flare. On the other hand, when performed by a non-specific specialist, positive skin prick tests to foods may wrongly lead to prolonged elimination diets, which may induce nutritional deficiencies and perhaps loss of tolerance to the avoided foods. Furthermore, skin prick tests increase health costs. A consensus on this topic has not yet been reached. Considering the diversity of clinical stages in which it occurs, atopic eczema presentation should be the starting point to determine whether or not skin prick tests should be carried out.

Pregnancy and birth cohort resources in europe: a large opportunity for aetiological child health research

BACKGROUND

During the past 25 years, many pregnancy and birth cohorts have been established. Each cohort provides unique opportunities for examining associations of early-life exposures with child development and health. However, to fully exploit the large amount of available resources and to facilitate cross-cohort collaboration, it is necessary to have accessible information on each cohort and its individual characteristics. The aim of this work was to provide an overview of European pregnancy and birth cohorts registered in a freely accessible database located at http://www.birthcohorts.net.

METHODS

European pregnancy and birth cohorts initiated in 1980 or later with at least 300 mother-child pairs enrolled during pregnancy or at birth, and with postnatal data, were eligible for inclusion. Eligible cohorts were invited to provide information on the data and biological samples collected, as well as the timing of data collection.

RESULTS

In total, 70 cohorts were identified. Of these, 56 fulfilled the inclusion criteria encompassing a total of more than 500,000 live-born European children. The cohorts represented 19 countries with the majority of cohorts located in Northern and Western Europe. Some cohorts were general with multiple aims, whilst others focused on specific health or exposure-related research questions.

CONCLUSION

This work demonstrates a great potential for cross-cohort collaboration addressing important aspects of child health. The web site, http://www.birthcohorts.net, proved to be a useful tool for accessing information on European pregnancy and birth cohorts and their characteristics.

Assessment of Total/Specific IgE Levels Against 7 Inhalant Allergens in Children Aged 3 to 6 Years in Seoul, Korea

PURPOSE

Childhood allergies are a serious problem, as they may lead to lifetime chronic disease. Determination of total and specific IgE levels is known to be a diagnostic tool for allergic sensitization; however, IgE levels are affected by various factors, such as age, sex, ethnicity, and geographic area. Thus, we evaluated the distribution of total and specific serum IgE levels against seven inhalant allergens in preschool children and examined their association with allergic diseases in Seoul, Korea.

METHODS

Total/specific serum IgE determination and skin prick tests for seven common allergens were performed on 509 children aged 3 to 6 years from 16 child care centers in Seoul, Korea. Demographic characteristics were surveyed from parents using a modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. A diagnosis of atopic dermatitis was made by physicians.

RESULTS

The geometric mean of total IgE was 80.48±3.80 kU/L in preschool children. IgE levels were higher in boys (boys, 102.34±3.52 kU/L; girls, 62.37±3.93 kU/L; P<0.001) and atopic subjects (atopic, 158.00±3.35 kU/L; non-atopic, 52.75±3.44 kU/L; P<0.001). An increased prevalence of atopy was associated with a high monthly household income (P=0.004) and higher maternal education level (above university-level education; P=0.009), as well as increased total IgE levels (P=0.036). Physician-diagnosed atopic dermatitis was associated with sensitization to inhalant allergens.

CONCLUSIONS

Total IgE levels were very high as compared with those in previous reports from other countries. The most common sensitized allergen was Dermatophagoides farinae, and the positive response rate peaked at age 3 years and was maintained thereafter, particularly in boys. Specific IgE levels for seven inhalant allergens varied with age in preschool children. Although further investigations are needed with a broad range of ages and various allergens, the distribution of the total and specific serum IgE levels in preschool children might help to serve as a reference value to diagnose atopy.

Environmental and demographic risk factors for egg allergy in a population-based study of infants

BACKGROUND

Although egg allergy is the most common food allergy in infants and young children, risk factors for egg allergy remain largely unknown. This study examined the relationship between environmental and demographic factors and egg allergy in a population-based infant cohort.

METHODS

In a study of 5276 infants (HealthNuts), infants underwent skin prick testing (SPT) to egg white at 12 months of age. Questionnaire data on relevant exposures were obtained. 699/873 (80%) infants eligible for oral food challenge (detectable wheal on SPT) attended for formal assessment of egg allergy status; 453 had confirmed egg allergy (positive challenge and SPT ≥ 2 mm). Associations between environmental and demographic factors and egg allergy were investigated using multivariable logistic regression.

RESULTS

Children with older siblings and those with a pet dog at home were less likely to develop egg allergy by 1 year of age (adjusted OR [aOR], 0.72; 95% CI, 0.62, 0.83 per sibling; and aOR, 0.72; 95% CI, 0.52, 0.99, respectively). Caesarean section delivery, antibiotic use in infancy, childcare attendance and maternal age were not associated with egg allergy. History of allergic disease in an immediate family member and having parents born in East Asia were strong risk factors for infantile egg allergy (aOR, 1.82; 95% CI, 1.40, 2.36; and aOR, 3.30; 95% CI, 2.45, 4.45, respectively).

CONCLUSIONS

Exposure in the first year of life to siblings and dogs may decrease the risk of subsequent egg allergy. Infants with a family history of allergy and those with parents born in East Asia are at increased risk of egg allergy.

The association between early sensitization patterns and subsequent allergic disease. The DARC birth cohort study

Prevention of allergic diseases depends on early identification of clinical markers preceding such disorders. This study describes the natural course of sensitization as measured by skin prick test (SPT) and specific immunoglobulin E (S-IgE) and analyses the association between early sensitization patterns and subsequent allergic disease at 6 yr of age. In an ongoing population-based birth cohort study of 562 children, follow-up visits were performed at 0, 3, 6, 9, 12, 18, 36, and 72 months. Visits included an interview, physical examination, SPTs, and S-IgE measurements for 12 food and inhalant allergens. The frequency of S-IgE sensitization to > or = 1 inhalant allergen was constant from 0 to 6 months (9-10%), decreased at 12-18 months before increasing from 36 months onwards. S-IgE sensitization to at least one food allergen remained constant from 0 to 6 yr. SPT sensitization to food and inhalant allergens appeared from 3 and 12 months, respectively. Early food sensitization (S-IgE) between 3 and 18 months was found to be significantly (p < 0.05) associated with atopic dermatitis (OR: 4.0 [1.6-9.9]) and asthma (OR 4.0 [1.1-12.5]) at the age of 6 yr. Children with atopic dermatitis, asthma, or rhinoconjunctivitis, and sensitization at 6 yr, were sensitized to food allergens to a large extent (53%, 42%, and 47%, respectively) already at 6 months. Early inhalant sensitization (S-IgE) did not increase the risk of later allergic disease. Early atopic dermatitis (0-18 months) was also highly associated with subsequent allergic disease. Children with early food sensitization and/or atopic dermatitis would be a proper target group for future interventional studies.

Skin prick tests and allergy diagnosis

Skin testing remains an essential diagnostic tool in modern allergy practice. A significant variability has been reported regarding technical procedures, interpretation of results and documentation. This review has the aim of consolidating methodological recommendations through a critical analysis on past and recent data. This will allow a better understanding on skin prick test (SPT) history; technique; (contra-) indications; interpretation of results; diagnostic pitfalls; adverse reactions; and variability factors.

Maternal smoking increases risk of allergic sensitization and wheezing only in children with allergic predisposition: longitudinal analysis from birth to 10 years

BACKGROUND

The role of passive smoking for allergies and asthma in children above the age of 3 years remains unclear and possible interactive effects with parental allergies have not been formally evaluated in long-term studies. To examine the interaction of passive smoking and an allergic predisposition regarding allergic sensitization, allergic airway symptoms and respiratory infections during the first 10 years of life.

METHODS

In a prospective multicenter birth cohort study with 1314 recruited children in Germany, we assessed serum immunoglobulin E against common allergens at seven time points, and parental smoking and respiratory symptoms annually by using questionnaires. Longitudinal analyses were performed using generalized estimating equation models (stratified by parental allergy status).

RESULTS

During the first 10 years, 18% of the children were exposed to regular maternal smoking since pregnancy, 43% to irregular maternal or only paternal smoking. Among children with two allergic parents, a mother who smoked regularly significantly increased the odds for allergic sensitization (adjusted OR 4.8, 95% CI 1.3-18.2) and wheezing (adjusted OR 5.7, 95% CI 1.7-19.0) in her child compared with children who were never exposed. For those with only one allergic parent, the odds were doubled and also statistically significant, whereas in children without allergic parents maternal smoking had no effects. There was no association of maternal smoking with allergic rhinitis or respiratory infections.

CONCLUSIONS

Our results suggest that regular maternal smoking is a strong risk factor for allergic sensitization and asthma symptoms during the first 10 years of life, but only in children with allergic parents.

Do boys do the atopic march while girls dawdle?

BACKGROUND

The atopic march hypothesis suggests that infants with eczema are at increased risk of asthma. Others argue that eczema is not a risk factor for asthma unless there is also sensitization or early wheezing.

OBJECTIVE

To examine the role of infantile eczema as a predictor of risk of childhood asthma, while allowing for the effects of early wheeze, sensitization, and sex, both as independent effects and possible effect modifiers.

METHODS

A total of 620 infants with a family history of allergic disease was recruited. Eczema and wheeze was prospectively documented to 2 years of age. Sensitization was determined by skin prick tests at 6, 12, and 24 months to 6 common food and inhalant allergens. Interviews were conducted at 6 and 7 years to ascertain current asthma.

RESULTS

Sufficiently complete data were available for 403 children. Eczema within the first 2 years of life was clearly associated with an increased risk of childhood asthma in boys (adjusted odds ratio, 2.45; 95% CI, 1.31-4.46) but not in girls (odds ratio, 0.88; 95% CI, 0.43-1.77; P for interaction = .031) even with adjustment for the effects of early allergic sensitization and wheeze. If these relationships are causal, an intervention to prevent eczema in boys might reduce the incidence of childhood asthma by as much as 28%.

CONCLUSION

Eczema in the first 2 years of life is associated with an increased risk of childhood asthma in boys, but there is no evidence of this in girls.

WITHDRAWN: Cow's milk protein avoidance and development of childhood wheeze in children with a family history of atopy

BACKGROUND

In infants with a family history of atopy, food allergen avoidance has been advocated as means of preventing the development of atopic disease, when breast-feeding is not possible or supplemental feeding is needed. Most infant formulas are based on cow's milk protein. Alternative choices include soya based and hydrolysed cows milk formulas.

OBJECTIVES

To estimate the effect of dietary avoidance of cow's milk protein on the development of asthma or wheeze in children.

SEARCH STRATEGY

We searched the Cochrane database for eligible trials until February 2002. We obtained the full text papers of all abstracts identified as RCTs and two reviewers independently reviewed them.

SELECTION CRITERIA

We included randomised controlled trials involving children with a family history of atopy in at least one first degree relative, if feeding with cow's milk based standard formula was compared to dietary avoidance of cow's milk protein, using soya or other hypoallergenic formula during the initial four months of life or longer.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data independently. A priori defined subgroups were the types of hypoallergenic artificial feed and dietary restrictions on mother and/or child's diet.

MAIN RESULTS

Six trials used hydrolysed formula for at least four months, in addition to dietary restrictions and in some cases dust-mite reduction measures. The risk of infants experiencing asthma or wheeze during the first year of life was reduced compared to standard cow's milk based formula (Relative Risk 0.40, 95% Confidence Intervals 0.19 to 0.85). Feeding soya-based formula as opposed to standard cow's milk formula did not reduce the risk of having asthma or wheeze at any age.

AUTHORS' CONCLUSIONS

Breast-milk should remain the feed of choice for all babies. In infants with at least one first degree relative with atopy, hydrolysed formula for a minimum of four months combined with dietary restrictions and environment measures may reduce the risk of developing asthma or wheeze in the first year of life. There is insufficient evidence to suggest that soya-based milk formula has any benefit.

Interactive effect of family history and environmental factors on respiratory tract-related morbidity in infancy

BACKGROUND

Family and environmental factors affect the development of respiratory morbidity. How these factors interact is unclear.

OBJECTIVE

We sought to clarify the interactive effect of family history of asthma and environmental factors on the occurrence of respiratory morbidity.

METHODS

Two hundred twenty-one infants with a positive family history of asthma (PFH) and 308 with a negative family history of asthma (NFH) were prenatally selected and followed until the age of 2 years. Exposure to environmental factors and the occurrence of respiratory morbidity were recorded. By using multiple logistic regression analysis, increased risk was expressed in odds ratios (ORs) adjusted for relevant covariables.

RESULTS

Infants with a PFH had more respiratory morbidity than infants with an NFH. Adjusted ORs ranged from 1.7 (95% CI, 1.0-2.8) for expiratory wheezing to 4.9 (95% CI, 1.7-13.6) for croup. Parental smoking increased the OR of a PFH for wheezing ever (OR, 5.8 [95% CI, 2.5-13.8]) and attacks of wheezing (OR, 6.8 [95% CI, 2.7-16.9]), as did Der p 1 (OR, 10.2 [95% CI, 2.8-36.3] and OR, 7.1 [95% CI, 7.1-21.0], respectively). Exposure to both parental smoking and Der p 1 further increased this OR (OR, 30.8 [95%, CI, 6.9-137.2] and OR, 26.2 [95% CI, 5.9-115.6], respectively). Breast-feeding decreased the ORs of PFH for tonsillitis and acute otitis media: the increased ORs for these diagnoses in formula-fed infants with PFHs versus those with NFHs (OR, 9.2 [95% CI, 2.1-39.7] and OR, 2.9 [95% CI, 1.1-7.2], respectively) was attenuated in breast-fed infants (OR, 1.8 [95% CI, 0.8-3.8] and OR, 0.7 [95% CI, 0.4-1.3]).

CONCLUSION

Parental smoking and Der p 1 increase the effect of a PFH on respiratory morbidity. Breast-feeding reduces this effect.

CLINICAL IMPLICATIONS

Extra attention should be given to stimulate mothers to breast-feed their children in case they cannot stop smoking or taking sanitation measures.

The temporal sequence of allergic sensitization and onset of infantile eczema

BACKGROUND

Eczema is commonly associated with sensitization in infants, but the causative role of sensitization in the development of eczema has been questioned.

OBJECTIVE

To determine if allergic sensitization increases the risk of developing eczema, or alternatively, if eczema increases the risk of developing allergic sensitization.

METHODS

We used data from the Melbourne Atopy Cohort Study, a prospective birth cohort of 552 infants with a family history of atopic disease. The main outcomes were risk of developing eczema from 6 months to 7 years of age in asymptomatic infants; and risk of developing sensitization, as measured by skin prick tests to milk, egg white, peanut, house dust mite, rye grass pollen and cat extracts, in previously unsensitized infants.

RESULTS

Sensitization to food extracts at 6 months was associated with an increased risk of developing eczema [hazard ratio (HR) 1.63, 95% confidence interval 1.13-2.35] up to 7 years of age, after excluding infants with eczema in the first 6 months. However, eczema in the first 6 months was also associated with increased risk of new sensitization at both 1 year (HR 2.34, 1.38-3.98) and 2 years (HR 3.47, 1.65-7.32).

CONCLUSION

In some infants, sensitization precedes and predicts the development of eczema, while in others eczema precedes and predicts the development of sensitization. This indicates that there are multiple pathways to atopic eczema.

The Paris prospective birth cohort study: Which design and who participates?

The Paris prospective birth cohort study was implemented in 2003 to assess environmental/behavioural factors associated with respiratory and allergic disorder occurrence in early childhood. This paper describes the design and sociodemographic features of eligible/enrolled families. Full-term newborns without any medical problem at birth were recruited in five Paris maternity hospitals. They resided in the Paris area and had French speaking mothers. Sample size is at least 3500 infants, and children are followed-up until their sixth birthday. Data collection is based on regular medical and environmental self-administered questionnaires to parents. Information on dwellings is gathered by means of phone questionnaires, and standardized medical examinations are carried out at 18 months and 6 years. Exposure to traffic-related pollution is modelled. At inclusion, some information concerning refusals is gathered in order to describe sociodemographic features of participating families as compared with eligible children. 4115 (63%) out of the 6493 eligible infants are now participating in this study. Participation rate is higher in parents with a high SES (socioeconomic status), for French and European parents, and for > or =25-year-old mothers, but decreases with sibship size. Similar determinants are associated with the distribution of reasons for non-participation. The participation rate in the Paris study is comparable with other similar studies. Finally, giving detailed explanation of the study aims at inclusion, establishing regular mailed and phoned contacts with families, offering free complete medical examinations for the participant child and re-sent missing questionnaires are very important to improve participation at inclusion and during follow-up.

Mold damage in homes and wheezing in infants

BACKGROUND

In most studies that investigate the association of mold or water damage and respiratory disorders in infants, the analysis is not adjusted for exposure to house dust mite (HDM), which is also a known cause of respiratory illnesses.

OBJECTIVE

To investigate the relationship between visually observable mold or water damage and HDM (Der f 1) levels and the prevalence of lower respiratory tract symptoms and allergen sensitization in infants of atopic parents as part of a prospective birth cohort study.

METHODS

On-site home visits (at the infants' age of 8 months) were performed to evaluate observable mold or water damage and HDM exposure. At a clinic visit near the infant's first birthday, medical histories, including parent-reported wheezing episodes, and a skin prick test to food and 15 common aeroallergens were conducted in 640 infants.

RESULTS

More than half of the homes were found to have mold or water damage, and 5% had major mold or water damage with visible mold at 0.2 m2 or more. Only 16% of homes had a HDM allergen (Der f 1) concentration of more than 2 microg/g. Major mold or water damage increased the risk of recurrent wheezing nearly 2 times in infants, 5 times in food or aeroallergen-sensitized infants, and 6 times in aeroallergen-sensitized infants. Neither visible mold or water damage nor HDM exposure was associated with sensitization to either mold or aeroallergens.

CONCLUSIONS

Visible mold was shown to be a significant risk factor for recurrent wheezing in infants at high risk of developing atopic disorders, whereas HDM exposure did not significantly increase the risk.

Wheezing, asthma, hayfever, and atopic eczema in childhood following exposure to tobacco smoke in fetal life

BACKGROUND

Prenatal maternal smoking has been associated with adverse respiratory effects in childhood such as lung deficits and wheezing, but results concerning asthma, hayfever, and atopic eczema are inconsistent.

OBJECTIVE

In the present study, we investigate the effects of maternal smoking in pregnancy on asthma, hayfever, atopic eczema, and wheezing in the offspring up to the age of 14-18.

METHODS

The study was based on a cohort of mothers enrolled during midwife visits around the 36th week of gestation in Odense and Aalborg, Denmark, 1984-1987. Singleton, live born children (n = 11,144) were followed-up in 2002 to obtain a childhood history of atopic diseases, by means of questionnaires to the parents. Multivariate logistic regression analyses for medical diagnoses of asthma, hayfever, atopic eczema, and symptoms of wheezing before the age of 3, were carried out on 7844 children.

RESULTS

After adjustment for confounders, late prenatal smoke exposure was associated with wheezing, with an odds ratio (OR) of 1.2, and a 95% confidence interval (CI) of 1.1-1.5. Furthermore, slightly reduced estimates for hayfever (OR 0.8, CI 0.7-1.0) and atopic eczema (OR 0.8, CI 0.7-0.9) were obtained for children exposed in late pregnancy compared with non-exposed.

CONCLUSION

Late gestational smoke exposure was associated with wheezing but not with asthma, while null or even protective estimates were indicated for hayfever and atopic eczema. However, lack of control options for hereditary factors may have affected the results.

Animal allergens

Animal allergen exposure in early childhood and its relationship to the development of atopic disease is a subject that has been evolving rapidly. Recently, several well-designed studies have helped elucidate previous, often conflicting findings on this topic. In addition, results from studies on farm-animal exposure have added strength to data on early dog and cat exposure. In this paper, we review several recent studies that have helped clarify the relationship between early animal-allergen exposure and childhood atopic disease.

Pets and the development of allergic sensitization

Sensitization to pets remains a risk factor for asthma and rhinitis, and can occur in people who have never lived with a pet. Several reports have indicated that living with a pet reduces the risk for becoming sensitized to that pet. Having a pet in the home gives exposure to more than just allergens. In areas with high frequency of pet ownership, community exposure to pet allergens is almost certainly sufficient to induce sensitization among non-pet owners. In this review, we examine the results of recent studies that have investigated the relationship between pet ownership, specific sensitization to that pet, and allergic sensitization in general. For cat ownership, the results are inconsistent between studies of similar design, with some studies suggesting an increase in risk and others a decrease among cat owners. For dogs, results are more consistent, generally suggesting that owning a dog has no effect or indeed may be protective against the development of specific sensitization to dog and allergic sensitization in general.

How atopic is atopic dermatitis?

BACKGROUND

The extent to which the phenotype of atopic dermatitis (AD) is truly atopic has been the subject of much debate.

OBJECTIVE

We sought to systematically evaluate the evidence for the value of measurement of IgE antibodies in diagnosing AD and whether knowledge of IgE sensitization increases clinical diagnostic and predictive ability.

METHODS

We searched Medline from its inception until September 2003. Only studies that measured atopy as either skin prick test positivity or IgE-antibody sensitization to environmental allergens were included within a descriptive analysis. Because the small number of studies of adequate quality did not allow a formal meta-analysis, we assigned strength of evidence according to predefined quality criteria and ranked studies accordingly.

RESULTS

Inclusion of atopy as part of the diagnostic criteria for AD did not enhance the criteria's sensitivity and specificity in relation to the clinical phenotype of AD. The strength of association between atopy and AD varied significantly between hospital studies (47% to 75%; n=14 studies) and was stronger in hospital than in community populations (7.4% to 78%; n=13 studies). Whereas study quality did not have an effect on atopy prevalence in hospital populations, low atopy prevalences in community surveys were seen in less rigidly conducted studies. AD severity was positively associated with the number of positive skin prick test responses or IgE-antibody levels in 7 of 8 studies that measured both. Only one study suggested that IgE-specific sensitization to hen's egg is associated with subsequent development of AD, and 2 studies found that allergen-specific IgE sensitization in patients with AD is a prognostic marker for allergic airway disease in later life. Atopy-associated AD might also have a worse long-term prognosis than AD that is not associated with atopy.

CONCLUSION

Although atopy is clearly associated with AD, the role of IgE sensitization in AD needs further study. Current evidence suggests that up to two thirds of persons with AD are not atopic, which implies that continued use of the term atopic dermatitis is problematic. Longitudinal studies are needed to compare the treatment response and prognosis of IgE-associated and non-IgE-associated AD.

Clinical value and measurement of specific IgE

The diagnosis of human allergic diseases involves the combined use of a careful clinical history, physical examination, and in vitro and in vivo assay methods for the detection of IgE antibodies of defined allergen specificities. In vivo (skin testing) and in vitro (measurement of specific IgE in serum) techniques cannot be considered interchangeable, the former reflecting not only the presence of IgE but also mast cell integrity, vascular and neural responsiveness. Both techniques have similarities and differences, advantages and disadvantages. Recently introduced "second generation" immunoassays have continued to improve the analytical sensitivity and reproducibility thanks to automation and improved reagent quality. Quantitative assays may allow the use of specific clinical thresholds able to differentiate symptomatic from asymptomatic patients. False-negative and false-positive results should derive from lability of some major extracts, and from possible cross-reactivities, respectively. Characterization of allergens at a molecular and submolecular level and, where necessary, the use of recombinant allergens can reduce cross-reactions and further improve the quality of immunoassays.

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.

[Prevention of asthma and allergic diseases in children]

Allergic diseases have become a major public health problem in industrialized countries, justifying the development of prevention programs. A review of the literature on allergens and atopic symptoms, age of primary sensitization and other factors associated with allergic diseases development is presented and is followed by a discussion on prevention measures. The most recent physiopathological and immunological data indicate that persistent asthma and allergic diseases in adults may be associated with events in early childhood. The parallel increase in autoimmune and allergic diseases has been correlated with regulatory mechanism defects, contradicting the previous theory that involved a predominantly Th1 or Th2 pathway. The primary prevention of asthma and allergic diseases thus appear to be somewhat utopian. Indeed based on recent results, the risk of developing allergies appears to be related to modern "clean" lyfestyles. Secondary prevention is probably necessary, possibly through specific immunotherapy. Tertiary prevention must also be considered. Passive smoking must be prevented as it can alter the development of the respiratory system and promote allergen sensitization. Randomized, controlled, prospective studies are needed to evaluate the efficacy of the preventive measures.

[Vaccination in children with egg allergy]

Vaccination of children who are allergic or assumed allergic to eggs still creates concern and complication for both the doctor and the patient. These concerns are based on a 1985 circular which has always been liberally interpreted and not well understood. Further analysis of the circular and a review of recent literature show, that most of the time, no special precautions need to be taken before vaccination of children with egg allergy.

Early pet exposure: friend or foe?

PURPOSE OF REVIEW

Sensitization to pets is a risk factor for asthma and it was assumed that pet ownership was a risk factor for sensitization. Epidemiological studies failed to confirm this, some even suggesting that keeping pets decreased the risk of sensitization and asthma. In the last year, 10 studies have been published which have, at least in part, attempted to address the question. The results, however, are heterogeneous and it is still not clear how we should advise our patients on this issue of pet ownership.

RECENT FINDINGS

Results of studies of the association between exposure to cat or cat allergen and the development of sensitization are such that almost any view on the relationship could be supported by evidence from the literature. For dogs, there are fewer data, but there is little to suggest that keeping a dog increases the risk of sensitization to dog. The majority of studies reviewed find either no association or a reduced risk of asthma amongst pet owners, but only one of these selectively excludes those who deliberately avoid pets from the analysis. There is evidence to suggest that amongst non-pet owners, the risk of sensitization and of asthma increases in areas with a high proportion of pet owners. There is evidence emerging that the effect of exposure to pets may be different in different relative risk groups, based on parental allergy. There is also evidence that asthma is more severe amongst pet sensitized pet owners.

SUMMARY

There are several large birth cohort studies being conducted around the world designed to measure the development of asthma and allergies in children with prospective and objective measures of environmental exposures. The results of such studies are required before the association between pets and asthma can be determined.

Do levels of immunoglobulin G antibodies to foods predict the development of immunoglobulin E antibodies to cat, dog and/or mite?

BACKGROUND

In children at high risk of inhalation allergy, food sensitization is associated with an increased risk for sensitization to inhalant allergens. Furthermore, this association was also found in a cross-sectional study.

OBJECTIVE

To examine in a prospective study, whether levels of IgG to foods (i.e. mixture of wheat and rice, mixture of soy bean and peanut, egg white, cow's milk, meat, orange and potato) indicate an increased risk for the future development of IgE antibodies to inhalant allergens in a low-risk population and whether they can be used as predictors of the subsequent development of IgE antibodies in young, initially IgE-negative children.

METHODS

Coughing children, aged 1-5, visiting their GPs, were tested for IgE antibodies to mite, dog and cat (RAST) and IgG (ELISA) to foods. All IgE-negative children were retested for IgE antibodies after two years. The IgG results (66 percentiles) of the first blood sample were compared to the RAST-scores of the second blood sample.

RESULTS

After two years, 51 out of 397 (12.8%) originally IgE-negative children, had become IgE-positive for cat, dog and/or mite. An increased IgG antibody level to wheat-rice (OR = 2.2) and to orange (OR = 2.0) indicated an increased risk of developing IgE to cat, dog or mite allergens. In addition to IgG to a mixture of wheat-rice and orange; total IgE, breastfeeding, eczema as a baby and age were the most important predictors for the subsequent development of IgE to inhalant allergens.

DISCUSSION

An increased IgG antibody level to a mixture of wheat-rice or orange, indicates an increased risk of developing IgE to cat, dog or mite allergens. This indicates that excessive activity of the mucosal immune system is present before IgE antibodies to airborne allergens can be demonstrated. Nevertheless, IgG to foods is not very helpful (with a positive predictive value of 16.5%, and negative predictive value of 90.6%) in identifying individual children at risk in clinical practice. However, besides other risk factors, IgG to wheat-rice and to orange could be useful as a screening test for studies in the early identification, i.e. before IgE antibodies can be detected, of children with an increased risk of developing IgE antibodies in the future.

Do animals on the farm and in the home reduce the risk of pediatric atopy?

Recent evidence suggests that proximity to pets and farm animals early in life may decrease the risk of developing atopy. Studies investigating the etiology of atopy and asthma have been especially challenging due to difficulties in ascertaining and classifying incident cases. Nevertheless, cross-sectional and cohort studies described in this paper reported across various populations, among children and adults, tended to demonstrate inverse associations between the presence of indoor cats and dogs or frequent exposure to livestock during the first years of life and sensitization to pet and pollen allergens, hay fever, and to a lesser degree, asthma. The biological mechanisms of this protection is unknown, as are the factors associated with pet keeping and livestock farming that may play a role. In the meantime, it appears that counseling prospective parents that avoidance of exposure to animals in the first years of life will prevent atopy may not be sage advice.

Which clinical subgroups within the spectrum of child asthma are attributable to atopy?

STUDY OBJECTIVES

The contribution of atopy to childhood asthma has been debated. We aimed to examine the relationship between atopy and asthma, taking into account differences in respiratory symptoms and disease severity.

DESIGN

A cross-sectional asthma survey involving the following: (1) a population sample of 758 (81% of eligible) school children aged 8 to 10 years from randomly selected schools in the Australian Capital Territory in 1999, and (2) a hospital-based sample of 78 (70% of eligible) children attending the hospital for asthma. Skin-prick test results to 10 common aeroallergens were available on 722 children and 77 children, respectively. Baseline spirometry was obtained on a subset of school children (n = 515, 78% of eligible).

RESULTS

The association between atopy and wheeze by wheeze frequency over the past year was as follows: no episodes (odds ratio [OR], 1.00 [reference]), 1 to 3 episodes (OR, 3.27; 95% confidence interval [CI], 2.15 to 4.97), 4 to 12 episodes (OR, 3.44; 95% CI, 1.75 to 6.75), and > 12 episodes (OR, 8.70; 95% CI, 3.07 to 24.55), with a higher population attributable fraction (PAF) for > 12 episodes (75%) than 1 to 3 episodes (49%). Atopy was moderately related to asthma ever (OR, 2.09; 95% CI, 1.52 to 2.85; PAF, 33%) but strongly related to 1999 hospital attendance for asthma (OR, 16.95; 95% CI, 6.76 to 42.48; PAF, 89%). Adjustment for child age, gas heater use, and maternal smoking near the child did not materially alter these findings.

CONCLUSIONS

The clinical features of frequent wheeze or hospital asthma attendance are largely attributable to atopy, but infrequent wheeze or a history of asthma ever are not. Atopic children are overrepresented in the severe range of the asthma spectrum.

Cow's milk protein avoidance and development of childhood wheeze in children with a family history of atopy

BACKGROUND

In infants with a family history of atopy, food allergen avoidance has been advocated as means of preventing the development of atopic disease when breast-feeding is not possible or supplemental feeding is needed. Most infant formulas are based on cow's milk protein. Alternative choices include soya based and hydrolysed cows milk formulas.

OBJECTIVES

To estimate the effect of dietary avoidance of cow's milk protein on the development of asthma or wheeze in children.

SEARCH STRATEGY

The Cochrane database was searched for eligible trials until February 2002. The full text papers of all abstracts identified as RCTs were obtained and reviewed independently by two reviewers.

SELECTION CRITERIA

Randomised controlled trials involving children with a family history of atopy in at least one first degree relative were considered if feeding with cow's milk based standard formula was compared to dietary avoidance of cow's milk protein using soya or other hypoallergenic formula during the initial four months of life or longer.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data independently. A priori defined subgroups were the types of hypoallergenic artificial feed and dietary restrictions on mother and/or child's diet.

MAIN RESULTS

Six trials used hydrolysed formula for at least 4 months in addition to dietary restrictions and in some cases dust-mite reduction measures. The risk of infants experiencing asthma or wheeze during the first year of life was reduced compared to standard cow's milk based formula (Relative Risk =0.40, 95% Confidence Intervals 0.19, 0.85). Feeding soya-based formula as opposed to standard cow's milk formula did not reduce the risk of having asthma or wheeze at any age.

REVIEWER'S CONCLUSIONS

Breast-milk should remain the feed of choice for all babies. In infants with at least one first degree relative with atopy, hydrolysed formula for a minimum of 4 months combined with dietary restrictions and environment measures may reduce the risk of developing asthma or wheeze in the first year of life. There is insufficient evidence to suggest that soya-based milk formula has any benefit.

Natural course of sensitization to cow's milk and hen's egg in childhood atopic dermatitis: ETAC study group

BACKGROUND

Sensitization to food allergens has been implicated in the pathogenesis of atopic diseases, in particular atopic dermatitis (AD). The aim of the present paper is to investigate the natural course of sensitization to egg and to cow's milk and its relationship with the severity of AD.

METHODS

The placebo intention-to-treat population of the ETACTM (Early Treatment of the Atopic Child) study consisted of 397 children with AD aged 12-24 months (mean+ SD: 17.2 + 4.1 months) who were followed for 18 months. All children were examined for objective SCORing Atopic Dermatitis (SCORAD) and specific IgE amongst other, to egg and to cow's milk at inclusion and after 3, 12 and 18 months. Fifteen patients were excluded from this analysis due to major protocol violations thus leaving 382 patients in the analysed population.

RESULTS

Sensitization to egg and to cow's milk was more common in atopic children with severe AD at all time-points. At inclusion, children sensitized to both egg and to cow's milk had the most severe AD (Kruskall-Wallis test P= 0.007). The degree of sensitization expressed in RAST classes was significantly related to the severity of AD. Furthermore, children sensitized to egg or to cow's milk at inclusion had a higher risk of persistence of AD (84% and 67%, respectively, vs. 57% in those not sensitized) and a higher objective SCORAD after 18 months follow-up.

CONCLUSION

We found an association between severity of AD and sensitization to egg or to cow's milk. Moreover, sensitization to egg, and to a lesser extent cow's milk, indicates a worse outcome of AD in terms of persistence and severity of the disease.

A double-blinded, randomized, placebo-controlled trial of cetirizine in preventing the onset of asthma in children with atopic dermatitis: 18 months' treatment and 18 months' posttreatment follow-up

BACKGROUND

Because asthma is not a curable condition, the development of strategies for prevention of the disease has a high priority. Atopic dermatitis is a common precursor to the development of asthma, and 2 studies have suggested that the use of an H(1) receptor antagonist might reduce the development of asthma while the treatment is being administered, at least in subgroups with evidence of high IgE levels. However, no trial to date has conducted follow-up after the initial treatment has been stopped to establish whether the intervention has merely suppressed symptoms or truly prevented disease.

OBJECTIVE

We sought to establish whether the use of cetirizine compared with placebo for 18 months in infants with atopic dermatitis suppressed or truly delayed the onset of asthma, even after cessation of therapy.

METHODS

The Early Treatment of the Atopic Child study was a double-blinded, parallel-group, randomized trial of 0.25 mg/kg body weight cetirizine administered twice daily compared with placebo given to infants between 1 and 2 years of age with atopic dermatitis. After 18 months of treatment, follow-up continued for a further 18 months. This article reports the outcome over the full 3 years of follow-up and relates the outcomes to the allergic status on the basis of IgE antibody measurements at recruitment.

RESULTS

Although there was no difference in cumulative prevalence of asthma between active and placebo treatment in the intention-to-treat population (P = .7), those infants with evidence of sensitivity to house dust mite, grass pollen, or both who were treated with cetirizine were significantly less likely to have asthma compared with those treated with placebo over the 18 months of treatment (P = .005 and .002, respectively), and this effect was sustained for the grass pollen-sensitized infants over the full 36 months (P = .008). In the house dust mite-sensitized group there was a gradual narrowing of the difference between active and placebo treatment in terms of cumulative prevalence of asthma at the end of 36 months but no evidence of a rebound immediately after the treatment stopped (P = .04). In the placebo population there was a significantly higher risk of development of asthma in those sensitized at baseline to egg (relative risk, 1.4 [95% CI, 1.1-1.7]), house dust mite (relative risk, 1.6 [95% CI, 1.3-1.9]), grass pollen (relative risk, 1.7 [95% CI, 1.4-2.1]), or cat (relative risk, 1.5 [95% CI, 1.2-1.9]). Early and persistent sensitization conferred a higher risk than transient or later sensitization.

CONCLUSIONS

Cetirizine compared with placebo truly delays or, in some cases, prevents the development of asthma in a subgroup of infants with atopic dermatitis sensitized to grass pollen and, to a lesser extent, house dust mite. Further studies are required focusing specifically on sensitized groups to substantiate this finding. The study also highlights risk factors for asthma in infants with atopic dermatitis and indicates that early and persistent aeroallergen sensitization confers a higher risk than later development of sensitivity.

Dog exposure in infancy decreases the subsequent risk of frequent wheeze but not of atopy

BACKGROUND

Influence of household pets in the development of childhood asthma or atopy has been controversial.

OBJECTIVE

The purpose of this study was to investigate whether pet exposure in early life decreases the subsequent risk of frequent wheezing and/or allergic sensitization.

METHODS

This was a prospective observational birth cohort study. The setting was a large health maintenance organization in Tucson, Ariz; the subjects were a population sample of 1246 newborns enrolled at birth and followed prospectively to age 13 years. The main outcome measures were as follows: time to first report of frequent wheezing (>3 episodes in the past year), skin prick test reactivity at 6 years and 11 years of age, and total serum IgE at 9 months, 6 years, and 11 years of age.

RESULTS

Children living in households with > or =1 indoor dogs at birth were less likely to develop frequent wheeze than those not having indoor dogs (P =.004). This inverse association was confined to children without parental asthma (hazard ratio = 0.47; P <.001 [Cox regression]) and was not evident for children with parental asthma (hazard ratio = 0.96; P =.87). Adjustment by potential confounders did not change the results. Indoor cat exposure was not significantly associated with the risk of frequent wheezing. Neither cat exposure in early life nor dog exposure in early life was associated with skin prick test reactivity or total serum IgE at any age.

CONCLUSION

Dog exposure in early life might prevent the development of asthma-like symptoms, at least in low-risk children with no family history of asthma. Nevertheless, early pet exposure does not seem to significantly influence the development of allergic sensitization.

Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: a randomised trial

BACKGROUND

Asthma places huge demands on health-care services, and its prevalence is increasing. Reduction of exposure to environmental allergens could offer a realistic chance for primary prevention. Our aim was to ascertain whether or not living in a low-allergen environment reduces the risk of asthma and atopic diseases in infants.

METHODS

We assigned infants to four risk groups according to parental atopic status. We enrolled 291 high-risk couples (both parents atopic, no pets) into a prospective, prenatally randomised, cohort study, and allocated them to environmental manipulation, in which measures to reduce prenatal and postnatal allergen exposure were undertaken (active HRA) (n=145) or no intervention (control HRC) (n=146). Two further prospective groups were studied: 161 high-risk infants with pets in the home (HRP group) and 168 low-risk infants, whose parents were both non-atopic (LR group). The main outcome measures were signs and symptoms of atopic disease at 1 year of age.

FINDINGS

103 families dropped out or were lost to follow up. At age 1 year we followed-up 133 HRA, 118 HRC, 140 HRP, and 126 LR infants. Children in the HRA group were less likely to have respiratory symptoms during the first year of life than those in the HRC group. The most pronounced differences were in the relative risks for severe wheeze with shortness of breath (relative risk 0.44 [95% CI 0.20-1.00]), prescribed medication for the treatment of wheezy attacks (0.58 [0.36-0.95]), and wheezing after vigorous playing, crying, or exertion (0.18 [0.04-0.79]). Probability of respiratory symptoms in HRC and HRP infants was similar, whereas it was much lower in the LR than in the HRC group. Cat ownership was significantly associated with sensitisation to cats (24.6 [3.04-199.05]; p=0.003).

INTERPRETATION

Environmental manipulation reduces some respiratory symptoms in the first year of life in high-risk infants. Further follow up is needed, however, to ascertain whether living in a low-allergen environment reduces allergy and asthma in later life.

Selective development of a strong Th2 cytokine profile in high-risk children who develop atopy: risk factors and regulatory role of IFN-gamma, IL-4 and IL-10

BACKGROUND

The immunological processes in early life and their relation to allergic sensitization leading to a Th2 cytokine profile are still not well understood.

OBJECTIVE

To analyse the environmental and genetic risk factors and immunological responses at birth in relation to the development of atopic disease at 12 months of age in a longitudinal study of high-risk children.

METHODS

High-risk children were followed from birth till 12 months of age. Mononuclear cells obtained at birth and 6 and 12 months thereafter were analysed for their proliferative and cytokine responses after polyclonal and allergen-specific stimulation.

RESULTS

At 12 months of age 25% children had developed an atopic disease. Two atopic parents, parental smoking and atopic dermatitis of at least one of the parents were significant risk factors. In cord blood of newborns who developed atopy, an increased percentage of CD4+CD45RO+ cells and an increased polyclonal-stimulated proliferation were observed. Furthermore, an impaired allergen-induced, but not polyclonal-stimulated IFN-gamma production was found, suggesting a regulatory defect. At 6 and 12 months of age, a strong Th2 profile (characterized by increased levels of IL-4, IL-5, and IL-13) after both polyclonal and, to a lesser extent, allergen-specific stimulation was found in the children developing atopy. Allergen-induced IL-10 production at 12 months of age was only observed in the non-atopic children.

CONCLUSION

Our data indicate that the first 6 months of life represent a critical time window for the initiation of immunological changes resulting in the development of atopy. The selective development of a Th2 cytokine profile in high-risk children who develop atopy is due to increased production of Th2 cytokines, possibly caused by impaired allergen-induced IFN-gamma production in the neonatal period. Furthermore, the decreased allergen-induced IL-10 levels observed in the atopic children at 12 months of age may result in a lack of down-regulation of the inflammatory process.

NAC Manchester Asthma and Allergy Study (NACMAAS): risk factors for asthma and allergic disorders in adults

Asthma and atopic disorders are the most common chronic diseases in the developed countries. Knowledge of the risk factors for these disorders may facilitate the development of preventive strategies aimed at reducing prevalence rates. To investigate the risk factors for asthma and allergic diseases in a large number of adults who are the parents of children in the National Asthma Campaign Manchester Asthma and Allergy Study. All pregnant women and their partners attending "Booking" antenatal clinics were invited to take part in the study. Questionnaire data were collected including the history of asthma and other atopic diseases, pet ownership and smoking habits, and skin prick tests were performed. The prevalence of atopy and the risk factors for asthma and allergic disorders were investigated in all subjects who completed the questionnaire and underwent skin testing. Statistical analysis was carried out using logistic regression. Initially, risk factors were assessed by univariate analysis to see how each potential explanatory variable affected the probability of having allergic disease. Variables were then tested in a forward stepwise multivariate analysis. In 5687 adult subjects there was a very high (48.2%) prevalence of atopy, and 9.7% of subjects had a diagnosis of asthma. In a multivariate regression analysis sensitization to dust mite, cat, dog and mixed grasses were all independently associated with asthma. The odds ratios for current asthma increased with the increasing number of positive skin tests (any two allergens - OR 4.3, 95% CI 3.3-5.5; any three allergens - OR 7.0 95% CI 5.3-9.3; all four allergens - OR 10.4, 95% CI 7.7-14; P < 0.00001). Dog ownership (OR 1.31, 95% CI 1.10-1.57; P = 0.003) and current smoking (OR 1.36, 95% CI 1.15-1.62; P = 0.0004) were significantly and directly associated with "asthma ever". Thirteen per cent of participants reported a history of eczema. In the multivariate analysis the strongest independent associate of eczema was sensitization to dog (OR 1.37, 95% CI 1.14-1.63, P < 0.0001). Apart from dog, the strength of the association between sensitization to common allergens and eczema appeared to be much lower than in the case of asthma. The prevalence of hay fever was high (20.6%), and in the multivariate analysis the association between sensitization to pollen and hay fever was extremely strong (OR 13.6, 95% CI 11.3-16.3; P < 0.0001). The results of the current study emphasize the importance of sensitization to indoor allergens in asthma. However, evidence of a possible direct role of allergen exposure in asthma causation remains unclear.

Airway responsiveness in early infancy predicts asthma, lung function, and respiratory symptoms by school age

Asthma is the most common chronic childhood disease in developed nations. Little is known about the relationship between airway responsiveness in infancy and the development of asthma later in life. The relationship of airway responsiveness at 1 mo with asthma, atopy, lower respiratory symptoms, and lung function at 6 yr of age was investigated prospectively in 95 white children from a randomly ascertained birth cohort. Baseline spirometry, airway responsiveness to histamine, and skin reactivity to common allergens were assessed at the age of 1 mo and 6 yr. Total serum immunoglobulin E (IgE) was measured from cord blood and at 6 yr. Blood eosinophil counts were measured at 6 yr only. Family, symptom, and exposure histories at both time points were derived from questionnaire data. Independently of the other factors assessed, increased airway responsiveness at 1 mo was significantly associated with the following parameters measured at six yr: decreased FEV(1) (p < 0.001); decreased FVC (p < 0.001); physician-diagnosed asthma (p < 0.001); and lower respiratory tract symptoms (p < 0.05). None of the other physiologic factors measured in infancy showed such consistent associations with important clinical and physiologic outcomes at age 6. These data suggest that airway responsiveness in early life defines a functional state that is associated with abnormal airway function, lower respiratory symptoms, and the emergence of asthma by 6 yr of age.