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

K-means cluster analysis of characteristic patterns of allergen in different ages: Real life study

BACKGROUND

Atopy varies in people of different ages owing to different physical conditions and exposure to allergens. We aimed to cluster ages based on atopic severity using K-means cluster analysis and identify atopic incidence, severity, as well as the association among peripheral eosinophils, IgE and sensitisation.

METHODS

Consecutive patients (n = 7654) with allergic symptoms and undergoing allergen-specific IgE tests were included from 2013 to 2017. Age, sex, specific-IgE, peripheral eosinophil counts and total-IgE were collected.

RESULTS

Five age categories were identified: 1-17, 18-36, 37-52, 53-69 and 70-100 years. The incidences of atopy and poly-sensitisation decreased with increasing age. Similar trend was observed for aeroallergens, egg and milk but not for peanuts, soy or seafood. Dust mites remain the crucial factor bothering patients with allergic symptoms, especially for children and adolescents. In patients aged <52 years, sensitisation to aeroallergens was more prevalent than food. In group 37-52 years, incidence of females' atopy was higher than that of males. The overlap of atopy, high eosinophils, and high total-IgE was found in only 19.18% of patients. The trend of allergen-test positivity is not parallel to total IgE and peripheral eosinophil counts.

CONCLUSION

Age-grouping based on cluster analysis helps to find the changes in atopic status and distribution of sensitised allergens with age. Allergen tests are still necessary in the clinical diagnosis and treatment. An innovative exploration of the influence of age and allergens on total-IgE and eosinophil counts is helpful for the development of bio-targeted precision therapy.

CLINICAL TRIAL REGISTRATION

ChiCTR2300067700.

Characteristics of children with cat sensitivity: a prospective cross-sectional study

BACKGROUND

Animal dander is one of the most common respiratory allergens in children, and there is evidence that cat sensitivity is a risk factor for asthma and allergic rhinitis. In this study, it was aimed to evaluate children with cat sensitivity and to identify their demographic and clinical characteristics.

METHODS

Patients who were found to be sensitive to cats following skin prick tests performed in our allergy clinic over a period of one year (and two control groups), were included in the study. Patients in the study and control groups filled in a questionnaire including demographic and clinical characteristics.

RESULTS

The prevalence of cat sensitivity in our allergy clinic was 6% (182/3033). The most common diagnoses in patients were 41.8% allergic rhinitis, 25.8% asthma, and 13.2% allergic rhinitis + asthma. Allergic rhinitis symptoms were the most prevalent symptom associated with cat contact (29.4%), whereas 28% of the patients were asymptomatic. Only 17.3% had a cat at home and 13.4% had cat exposure apart from home but having a cat at home was significantly higher than the control groups (p < 0.05). Eosinophilia was present in 54.6% of the patients, and 17.3% had blood tIgE levels of >1000 IU/mL. Eosinophilia and tIgE levels were significantly higher than both control groups (p < 0.05).

DISCUSSION

Cat ownership can affect the development of cat sensitivity but the majority of patients with cat sensitivity are not cat owners. Elevated tIgE levels (> 1000 IU/mL) may be associated with cat sensitivity, these patients should be evaluated for cat sensitivity, even if they do not report symptoms with cat contact.

The association of timothy grass allergy and cat ownership on cat sensitization

Background: Pollen hypersensitivity might be a determining factor for other nonseasonal allergens because it may indicate deviation of the immune system toward T-helper type 2 activity and immunoglobulin E sensitivity. Objective: To investigate whether timothy grass pollen allergy may be a predictive factor for cat sensitization and whether there is an association between sensitivity to both allergens. Method: A retrospective review was made of patients with symptoms of rhinitis. The skin-prick test results and cat ownership status of the patients were analyzed. On the basis of the skin-prick test results with Phleum pratense (timothy grass) and other pollens, the patients were analyzed in two groups: "timothy allergic" and "non-timothy allergic." Results: A total of 383 patients with the diagnosis of rhinitis were included in the study, which comprised 213 (55.6%) in the timothy allergic group and 170 (44.4%) in the non-timothy allergic group. The frequency of cat sensitization was significantly higher in the patients in the timothy allergic group compared with those without timothy grass allergy (33.8% versus 12.3%; p < 0.001). No significant difference was determined between the two groups in terms of cat ownership (p = 0.63). In the logistic regression analysis, cat ownership (adjusted odds ratio [OR] 23.07 [95% confidence interval {CI}, 7.72-68.91]) and timothy allergy (adjusted OR 7.72 [95% CI, 3.16-18.86]) were associated with an increased risk of cat sensitization. Conclusion: Timothy grass allergy may play a role in the development of cat sensitization; however, further research is needed to clarify these associations and the underlying mechanisms.

Age Differences in Pet Sensitization by Pet Ownership

OBJECTIVES

The association between pet sensitization and pet ownership remains unclear. Therefore, we aimed to elucidate the association between pet sensitization and pet ownership by age.

METHODS

We retrospectively reviewed 2,883 patients who visited our allergy clinic for nasal symptoms from January 2003 to December 2014, of whom 1,957 patients with data on skin-prick tests and questionnaire responses were included and divided into adults (age >19 years) and children (age ≤19 years). The association between pet sensitization and pet ownership was evaluated in both groups.

RESULTS

Among children, dog and cat sensitization showed no associations with dog and cat ownership, respectively. However, among adults, dog sensitization was significantly associated with dog ownership (odds ratio [OR], 3.283; P<0.001), and cat sensitization with cat ownership (OR, 13.732; P<0.001). After adjustment for age, sex, familial history of allergy, sinusitis, diabetes mellitus, other pet ownership, and non-pet sensitization, significant associations remained between dog sensitization and dog ownership (adjusted OR [aOR], 3.881; P<0.001), and between cat sensitization and cat ownership (aOR, 10.804; P<0.001) among adults. Dog ownership did not show any association with allergic rhinitis, asthma, or atopic dermatitis, whereas atopic dermatitis had a significant association with cat ownership in adults (aOR, 4.840; P<0.001).

CONCLUSION

Pet ownership in adulthood increased the risk of pet sensitization. However, pet ownership was not associated with the prevalence of atopic disorders, regardless of age, except for atopic dermatitis and cat ownership in adults.

IgE recognition profile of aeroallergen components in young children sensitized to dogs

Background

Pet ownership is increasing rapidly and as growing numbers of dogs in household, clinicians are facing more allergic patients and so as in young children.

Objective

This study aims to profile the IgE recognition patterns to aeroallergen components in young children sensitized to dogs.

Methods

Through retrospective chart reviews, we evaluated the clinical, environmental, and laboratory findings of patients sensitized to dogs in early life. We further evaluated specific IgE to dog component allergens (Can f 1, Can f 2, and Can f 3) and other aeroallergens using a microarray.

Results

The median age of 28 patients sensitized to dogs (dog-specific IgE ≥ 0.35 kU/L; 0.38–101 kU/L) was 61 months and underlying diseases included doctor diagnosed atopic dermatitis (n = 17), asthma (n = 7), and allergic rhinitis (n = 5). Twenty patients (71.4%) had experienced self-reported dog allergy and 70.0% of them were symptomatic after exposed to dogs from others. Component-resolved diagnosis was performed on 18 patients. Can f 1 positivity was the most common (77.8%) but had no value in symptom prediction. The most common cosensitized aeroallergen was house dust mites (44.5%). The symptomatic group tended to be poly-sensitized to Can f 1, Can f 2, and Can f 3.

Conclusion

Can f 1 was dominantly detected and poly-sensitized to Can f 2 and/or Can f 3 simultaneously tend to develop hypersensitivity to dogs in young children. Most of them were exposed to dogs not living with.

Effect of Exposure to Cats and Dogs on the Risk of Asthma and Allergic Rhinitis: A Systematic Review and Meta-analysis

BACKGROUND

Controversies persist regarding whether exposure to cat or dog increases the risk of asthma and allergic rhinitis.

OBJECTIVE

This meta-analysis aimed to assess the associations between exposure to cats or dogs and the development of asthma and allergic rhinitis.

METHODS

A systematic review was performed to identify case-control and cohort studies before May 2019, evaluating the association between exposure to cats and dogs and the risk of asthma and rhinitis. The risk of bias was assessed using the Newcastle-Ottawa Scale. The odds ratios (ORs) and risk ratios (RRs) were pooled for case-control and cohort studies, respectively. Subgroup analyses were performed on prespecified study-level characteristics.

RESULTS

The meta-analysis of 34 cohort studies showed a protective role of exposure to cats [RR: 0.88, 95% confidence interval (CI): 0.77-0.99] or dogs (RR: 0.85, 95% CI: 0.73-0.97) in the development of asthma. The subgroup analysis of birth cohort (RR: 0.74, 95% CI: 0.56-0.93) and children population (RR: 0.83, 95% CI: 0.70-0.96) also suggested a favorable role of exposure to dogs in the development of asthma. Pooled evidence from 13 case-control studies indicated no significant impact of cats (OR: 1.66, 95% CI: 0.39-2.94) and dogs (OR: 1.22, 95% CI: 0.92-1.52) on the development of asthma. A pooled analysis of five cohort studies showed a favorable effect of exposure to cats (RR: 0.60, 95% CI: 0.33-0.86) or dogs (RR: 0.68, 95% CI 0.44-0.90) on the development of allergic rhinitis.

CONCLUSION

The findings indicated a protective effect of exposure to cats and dogs, especially ownership, on the development of asthma and allergic rhinitis.

Immunization of cats to induce neutralizing antibodies against Fel d 1, the major feline allergen in human subjects

BACKGROUND

Cat allergy in human subjects is usually caused by the major cat allergen Fel d 1 and is found in approximately 10% of the Western population. Currently, there is no efficient and safe therapy for cat allergy available. Allergic patients usually try to avoid cats or treat their allergy symptoms.

OBJECTIVE

We developed a new strategy to treat Fel d 1-induced allergy in human subjects by immunizing cats against their own major allergen, Fel d 1.

METHODS

A conjugate vaccine consisting of recombinant Fel d 1 and a virus-like particle derived from the cucumber mosaic virus containing the tetanus toxin-derived universal T-cell epitope tt830-843 (CuMVTT) was used to immunize cats. A first tolerability and immunogenicity study, including a boost injection, was conducted by using the Fel-CuMVTT vaccine alone or in combination with an adjuvant.

RESULTS

The vaccine was well tolerated and had no overt toxic effect. All cats induced a strong and sustained specific IgG antibody response. The induced anti-Fel d 1 antibodies were of high affinity and exhibited a strong neutralization ability tested both in vitro and in vivo. A reduction in the endogenous allergen level and a reduced allergenicity of tear samples, were observed.

CONCLUSION

Vaccination of cats with Fel-CuMVTT induces neutralizing antibodies and might result in reduced symptoms of allergic cat owners. Both human subjects and animals could profit from this treatment because allergic cat owners would reduce their risk of developing chronic diseases, such as asthma, and become more tolerant of their cats, which therefore could stay in the households and not need to be relinquished to animal shelters.

Increasing Prevalence of the Sensitization to Cat/Dog Allergens in Korea

Background

Recently, the number of domestic pets has increased. As a consequence, sensitization to animal allergens, such as cat or dog allergens, has become a problem.

Objective

We studied the annual trends of sensitization to cats or dogs, and the characteristics of the patients.

Methods

We retrospectively analyzed the medical records of 7,469 patients who visited a dermatology clinic and underwent an allergic profile test, from January 2011 to December 2015. Specific immunoglobulin E (IgE) levels to cat or dog antibody greater than 3.50 IU/ml were regarded as positive results.

Results

In all, 274 patients showed significant increase in levels of specific IgE antibody to dog, and 307 revealed increase in levels of of specific IgE antibody to cat. The prevalence of these specific IgEs increased from 2011 to 2015. Independent risks for sensitization to cat allergens were sensitization to dog, but not to house dust, Dermatophagoides pteronyssinus, and D. farinae. Independent risks for sensitization to dog allergens were sensitization to cat, but not to house dust, D. pteronyssinus, and D. farinae. Total IgE level was not related to specific IgE level against either cats or dogs.

Conclusion

In conclusion, the prevalence of sensitization to cat or dog has increased. Sensitization to cat or dog is related to each other, but is irrelevant to the total IgE level.

Excision release of 5?hydroxycytosine oxidatively induced DNA base lesions from the lung genome by cat dander extract challenge stimulates allergic airway inflammation

BACKGROUND

Ragweed pollen extract (RWPE) induces TLR4-NFκB-CXCL-dependent recruitment of ROS-generating neutrophils to the airway and OGG1 DNA glycosylase-dependent excision of oxidatively induced 8-OH-Gua DNA base lesions from the airway epithelial cell genome. Administration of free 8-OH-Gua base stimulates RWPE-induced allergic lung inflammation. These studies suggest that stimulation of innate receptors and their adaptor by allergenic extracts initiates excision of a set of DNA base lesions that facilitate innate/allergic lung inflammation.

OBJECTIVE

To test the hypothesis that stimulation of a conserved innate receptor/adaptor pathway by allergenic extracts induces excision of a set of pro-inflammatory oxidatively induced DNA base lesions from the lung genome that stimulate allergic airway inflammation.

METHODS

Wild-type (WT), Tlr4KO, Tlr2KO, Myd88KO, and TrifKO mice were intranasally challenged once or repeatedly with cat dander extract (CDE), and innate or allergic inflammation and gene expression were quantified. We utilized GC-MS/MS to quantify a set of oxidatively induced DNA base lesions after challenge of naïve mice with CDE.

RESULTS

A single CDE challenge stimulated innate neutrophil recruitment that was partially dependent on TLR4 and TLR2, and completely on Myd88, but not TRIF. A single CDE challenge stimulated MyD88-dependent excision of DNA base lesions 5-OH-Cyt, FapyAde, and FapyGua from the lung genome. A single challenge of naïve WT mice with 5-OH-Cyt stimulated neutrophilic lung inflammation. Multiple CDE instillations stimulated MyD88-dependent allergic airway inflammation. Multiple administrations of 5-OH-Cyt with CDE stimulated allergic sensitization and allergic airway inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE

We show for the first time that CDE challenge stimulates MyD88-dependent excision of DNA base lesions. Our data suggest that the resultant-free base(s) contribute to CDE-induced innate/allergic lung inflammation. We suggest that blocking the MyD88 pathway in the airways with specific inhibitors may be a novel targeted strategy of inhibiting amplification of innate and adaptive immune inflammation in allergic diseases by oxidatively induced DNA base lesions.

Cat ownership is associated with increased asthma prevalence and dog ownership with decreased spirometry values

The association between pet ownership and the development of allergic and respiratory diseases has been the aim of several studies, however, the effects of exposure in adults remain uncertain. The aims of the present study were to investigate the prevalence of asthma and lung function status among dog and cat owners. This cross-sectional study was performed at two universities with students and workers who were allocated into 3 groups according to pet ownership in the previous year: cat owners, dog owners, and no pets (control group). Subjects underwent spirometry, bronchial challenge test with mannitol, skin prick tests, and questionnaires about animal exposures and respiratory symptoms. Control group comprised 125 subjects; cat owner group, 51 subjects; and dog owner group, 140 subjects. Cat owners had increased asthma prevalence (defined by symptoms and positive bronchial challenge test), but no changes in lung function compared to the control group. The dog owner group had lower spirometry values (forced expiratory volume in one second and lower forced vital capacity), but similar asthma prevalence, compared to the control group. In the cat owner group, excess of asthma may have an immunological basis, since we found an association with atopy. Although we did not have endotoxin data from volunteers' households, we postulated that low values of lung function were associated to exposure to endotoxins present in environments exposed to dogs.

SLIT's Prevention of the Allergic March

PURPOSE OF REVIEW

The progression of atopic disorders from atopic dermatitis in infants to allergic rhinitis and asthma in children, adolescents, and adults defines the allergy march. Allergen immunotherapy is the only causal treatment altering the immunological mechanism underlying the allergic diseases. The sublingual administration route is more acceptable than the subcutaneous one in pediatric age.

RECENT FINDINGS

Several studies show the efficacy and safety profile of sublingual immunotherapy (SLIT) for the treatment of respiratory allergy diseases, but few data are available on its effect of primary and secondary prevention of allergic disease. The purpose of this manuscript is to review the latest studies addressing the effect of SLIT on the development of new sensitizations in not sensitized or already sensitized patients and progression of the allergy march.

Racial differences in pet ownership in families of children with asthma

BACKGROUND

Exposure to household domestic animals such as cats and dogs in early life may have some role in pathogenesis of asthma. Racial differences exist in the prevalence of asthma. We hypothesized that there may also be racial differences in pet ownership in families with asthma.

METHODS

A cross sectional study was conducted from June 2011 to December 2014 on 823 of 850 (97%) families of children with asthma for pet ownership. Comparisons among racial groups were done using chi square analysis and one-way analysis of variance.

RESULTS

The mean age of the cohort was 6.9±4.4 years. A total of 540 (65.62%) patients were Caucasian, 195 (23.7%) African American, 42 (5.1%) hispanics, and 26 (3.2%) biracial with one Caucasian parent. Pets in the home were reported by 470 (58.5%) households. Significantly fewer African American and hispanic families had pets in the home (26.9% and 44.7%) than biracial and Caucasian families (72% and 69.9%, P<0.001). Likewise, significantly more biracial and Caucasian families were noted to have dogs (52% and 54.4%) or cats (25.4% and 40%) or both cats and dogs (28% and 18%) than African Americans families (20.3%, P<0.001; 7.1%, P<0.001) and (4.6%, P<0.001), respectively.

CONCLUSIONS

Among families with asthmatic children, pet ownership is significantly more likely in Caucasian families compared with African-American and Hispanic families, thus there is a racial diversity in pet ownership among families of children with asthma.

Fractionation of Source Materials Leads to a High Reproducibility of the SQ House Dust Mite SLIT-Tablets

BACKGROUND

The production of house dust mite (HDM) allergen products for allergy immunotherapy has traditionally been based on purified mite bodies or whole-mite culture, which are quite different source materials with a limited possibility for adjusting the chemical composition. The SQ HDM SLIT-tablet is a fast-dissolving pharmaceutical formulation that has been developed for sublingual immunotherapy (SLIT) of HDM respiratory allergic disease.

OBJECTIVE

The objective of the present study was to establish a process for the production of drug substances for the SQ HDM SLIT-tablet offering a high reproducibility and independent control of the major allergens.

METHODS

Process controls were documented in a comprehensive process parameter qualification. The analyses comprised composition by crossed immunoelectrophoresis, protein content by BCA, total IgE binding potency by Centaur assay, quantitative major allergen determination by radial immunodiffusion and ELISA, and the ranking of emPAI scores generated by mass spectrometry.

RESULTS

Analysis of 20 batches of final product yielded a normalized mean and standard deviation for IgE binding potency of 100 ± 4.5. The standard deviation in the contents of Der f 1 and Der p 1 were correspondingly 11.9 and 6.1, whereas the variation in the group 2 major allergen content was 6.4. All measured 95% confidence limits between batches were less than 12%.

CONCLUSIONS

The production process for the SQ HDM SLIT-tablet based on the separation of source material into four fractions each enriched in one major allergen enables precise adjustment of the relative major allergen content and high reproducibility of the final product.

Allergy immunotherapy: the future of allergy treatment

Allergic respiratory disease represents a significant and expanding health problem worldwide. Allergic symptoms, such as asthma and hay fever, cause sleep impairment and reduce school and work performance. The cost to society is substantial. Allergen avoidance and pharmacotherapy cannot control the disease. Only allergy immunotherapy has disease-modifying potential and should be included in optimal treatment strategies. Allergy immunotherapy was first administered as subcutaneous injections and has been practiced for the past 100 years or so. Recently, tablet-based sublingual allergy immunotherapy (SLIT) was introduced with comprehensive clinical documentation. SLIT tablets represent a more patient-friendly concept because they can be used for self-treatment at home.

IgE antibodies to alpha-gal in the general adult population: relationship with tick bites, atopy, and cat ownership

BACKGROUND

The carbohydrate alpha-gal epitope is present in many animal proteins, including those of red meat and animal immunoglobulins, such as cat IgA. Systemic anaphylaxis to the alpha-gal epitope has recently been described.

OBJECTIVE

To investigate and compare the prevalence of alpha-gal-specific (s)IgE and its associated factors in the general adult population from two separated (Northern and Southern) European regions (Denmark and Spain, respectively).

METHODS

Cross-sectional study of 2297 and 444 randomly selected adults from 11 municipalities in Denmark and one in Spain. Alpha-gal sIgE was assessed by ImmunoCAP to bovine thyroglobulin. Additional assessments included a panel of skin prick test (SPT) to common aeroallergens and epidemiological factors, including the history of tick bites in the Danish series.

RESULTS

The prevalence of positive (≥ 0.1 kUA /L) sIgE to alpha-gal was 5.5% and 8.1% in the Danish and Spanish series, respectively. The prevalence of sIgE ≥ 0.35 kUA /L was 1.8% and 2.2% in Denmark and Spain, respectively. Alpha-gal sIgE positivity was associated with pet ownership in both series and, particularly, cat ownership (data available in the Danish series). Alpha-gal sIgE positivity was associated with atopy (SPT positivity) in both series, although it was not associated with SPT positivity to cat or dog dander. Alpha-gal sIgE positivity was strongly associated with a history of tick bites.

CONCLUSIONS AND CLINICAL RELEVANCE

The prevalence of alpha-gal sIgE antibodies in these general adult European populations is similarly low. The presence of alpha-gal sIgE antibodies is associated with a history of tick bites, atopy, and cat ownership.

Allergy to furry animals: New insights, diagnostic approaches, and challenges

The prevalence of allergy to furry animals has been increasing, and allergy to cats, dogs, or both is considered a major risk factor for the development of asthma and rhinitis. An important step forward in the diagnosis of allergy to furry animals has been made with the introduction of molecular-based allergy diagnostics. A workshop on furry animals was convened to provide an up-to-date assessment of our understanding of (1) the exposure and immune response to the major mammalian allergens, (2) the relationship of these responses (particularly those to specific proteins or components) to symptoms, and (3) the relevance of these specific antibody responses to current or future investigation of patients presenting with allergic diseases. In this review research results discussed at the workshop are presented, including the effect of concomitant exposures from other allergens or microorganisms, the significance of the community prevalence of furry animals, molecular-based allergy diagnostics, and a detailed discussion of cat and dog components.

Association between pet ownership and the sensitization to pet allergens in adults with various allergic diseases

Purpose

As pet ownership increases, sensitization to animal allergens due to domestic exposure is a concern. Sensitization to animal allergens may occur from indirect exposure, as well as direct ownership of animals. However, there have been conflicting results regarding the association between pet ownership and sensitization to animal allergens in adults.

Methods

In total, 401 patients with various allergic diseases were enrolled in this study. We performed skin prick tests with 55 common inhalant and food allergens, including dog, cat, and rabbit allergens. A mean wheal diameter of 3 mm or greater was considered a positive reaction. The exposure modality to each animal allergen was investigated using a questionnaire and included present ownership, past ownership, occupational exposure, occasional exposure, contact with pet owner, and no contact. Present ownership, past ownership, occupational, and occasional exposure were regarded as direct exposure.

Results

The sensitization rate for animal allergens was 20.4% for dog, 15.0% for cat, and 9.0% for rabbit. Direct exposure to dogs (72.0%) was significantly higher than that of other animals (18.4% for cats and 16.7% for rabbits), whereas 'no contact' with cats (78.3%) and rabbits (83.3%) was significantly higher than with dogs (26.8%; P<0.0001). Independent risk factors for sensitization to animal allergens were sensitization to Dermatophagoides pteronyssinus (OR=2.4, P=0.052), Dermatophagoides farinae (OR=5.1, P<0.001), cat (OR=4.4, P<0.0001), and direct exposure to dogs (OR=1.5, P=0.029) for dog, and sensitization to dog (OR=4.4, P<0.0001) and rabbit (OR=2.6, P=0.036) for cats. Finally, for rabbits, the independent risk factor was sensitization to Alternaria (OR=6.0, P<0.002).

Conclusions

These results suggest that direct exposure to dogs contributes to the sensitization to dog allergens in patients with allergic diseases, whereas indirect exposure to cats and rabbits may induce sensitization to each animal's allergen.

Dog saliva - an important source of dog allergens

BACKGROUND

Allergy to dog (Canis familiaris) is a worldwide common cause of asthma and allergic rhinitis. However, dander extract in routine diagnostics is not an optimal predictor of IgE-mediated dog allergy. Our objective was to evaluate saliva as an allergen source for improved diagnostics of allergy to dog.

METHODS

IgE-binding proteins in dog saliva and dander extract were analysed by immunoblot and mass spectrometry (LC-MS/MS) using pooled or individual sera from dog-allergic patients (n = 13). Sera from 59 patients IgE positive to dander and 55 patients IgE negative to dander but with symptoms to dog were analysed for IgE against saliva and dander by ELISA. Basophil stimulation with dog saliva and dander extract was measured by flow cytometry among three dog-allergic patients. Additionally, IgE-binding protein profiles of saliva from different breeds were investigated by immunoblot.

RESULTS

Greater number and diversity of IgE-binding proteins was found in saliva compared to dander extract and varied among dog breeds. In saliva, Can f 1, 2, 3 and 6 were identified but also four new saliva allergen candidates. The majority of the 59 dog dander-positive sera (n = 44) were IgE positive to dog saliva. Among patients IgE negative to dander, but with symptoms to dog, 20% were IgE positive to saliva. The biological activity of saliva was confirmed by basophil degranulation.

CONCLUSIONS

Dog saliva is an allergen source for improved diagnostics of dog allergy. The IgE-binding protein profile of saliva from different dogs varies.

Allergen-specific immunotherapy provides immediate, long-term and preventive clinical effects in children and adults: the effects of immunotherapy can be categorised by level of benefit -the centenary of allergen specific subcutaneous immunotherapy

Allergen Specific Immunotherapy (SIT) for respiratory allergic diseases is able to significantly improve symptoms as well as reduce the need for symptomatic medication, but SIT also has the capacity for long-term clinical effects and plays a protective role against the development of further allergies and symptoms. The treatment acts on basic immunological mechanisms, and has the potential to change the pathological allergic immune response. In this paper we discuss some of the most important achievements in the documentation of the benefits of immunotherapy, over the last 2 decades, which have marked a period of extensive research on the clinical effects and immunological background of the mechanisms involved. The outcome of immunotherapy is described as different levels of benefit from early reduction in symptoms over progressive clinical effects during treatment to long-term effects after discontinuation of the treatment and prevention of asthma. The efficacy of SIT increases the longer it is continued and immunological changes lead to potential long-term benefits. SIT alone and not the symptomatic treatment nor other avoidance measures has so far been documented as the therapy with long-term or preventive potential. The allergic condition is driven by a subset of T-helper lymphocytes (Th2), which are characterised by the production of cytokines like IL-4, and IL-5. Immunological changes following SIT lead to potential curative effects. One mechanism whereby immunotherapy suppresses the allergic response is through increased production of IgG4 antibodies. Induction of specific IgG4 is able to influence the allergic response in different ways and is related to immunological effector mechanisms, also responsible for the reduced late phase hyperreactivity and ongoing allergic inflammation. SIT is the only treatment which interferes with the basic pathophysiological mechanisms of the allergic disease, thereby creating the potential for changes in the long-term prognosis of respiratory allergy. SIT should not only be recognised as first-line therapeutic treatment for allergic rhinoconjunctivitis but also as secondary preventive treatment for respiratory allergic diseases.

Risk factors for new-onset cat sensitization among adults: a population-based international cohort study

BACKGROUND

Cat exposure during childhood has been shown to increase the risk of developing cat sensitization, while the effect of cat exposure in adulthood has not yet been established.

OBJECTIVE

To evaluate new-onset sensitization to cat in adulthood in relation to changes in cat keeping.

METHODS

A total of 6292 European Community Respiratory Health Survey I (ECRHS I) participants aged 20 to 44 years from 28 European centers, who were not sensitized to cat, were reevaluated 9 years later in ECRHS II. Present and past cat ownership and total and specific IgE levels were assessed in both surveys. Allergen-specific sensitization was defined as a specific serum IgE level of 0.35 kU/L or more.

RESULTS

A total of 4468 subjects did not have a cat in ECRHS I or ECRHS II, 473 had a cat only at baseline, 651 acquired a cat during the follow-up, and 700 had a cat at both evaluations. Two hundred thirty-one subjects (3.7%) became sensitized to cat. In a 2-level multivariable Poisson regression model, cat acquisition during follow-up was significantly associated with new-onset cat sensitization (relative risk = 1.85, 95% CI 1.23-2.78) when compared with those without a cat at both surveys. Preexisting sensitization to other allergens, a history of asthma, nasal allergies and eczema, and high total IgE level were also significant risk factors for developing cat sensitization, while cat ownership in childhood was a significant protective factor.

CONCLUSION

Our data support that acquiring a cat in adulthood nearly doubles the risk of developing cat sensitization. Hence, cat avoidance should be considered in adults, especially in those sensitized to other allergens and reporting a history of allergic diseases.

Contact to cat or dog, allergies and parental education

Whether or not associations between animal contact and allergy/atopy are homogeneous across social strata has not yet been investigated. The aim of this study was to estimate the association between animal contact (cat, dog) and allergy/atopy in 6-yr-old school beginners, stratified by parental educational level. A total of 30794, 6-yr old children participated in cross-sectional studies between 1991 and 2000 in Germany. Allergic sensitization to common aeroallergens and symptoms and diagnoses of atopic diseases (asthma, eczema, hay fever) were the dependent variables. Contact with dog/cat were the independent variables. Logistic regression was used to adjust for confounding. Analyses were stratified for parental education. Prevalences of hay fever, eczema, specific sensitization to pollen and house dust mite increased, while the prevalence of contact to cat and dog decreased with parental educational level. Globally significant positive associations between cat contact and sensitization to cat (interaction significant) and between dog contact and wheezing remained significant in the highest and medium/highest educational strata respectively. A globally significant inverse association between cat contact and hay fever remained significant in the highest educational stratum only. The inverse association of contact to dog with eczema was globally significant, but not in the strata. When estimating the associations between animal contact and allergy/atopy in children, effect modification by social status should be considered. Cat contact seems to increase the odds of sensitization to cat only in children whose parents have a high level of education.

The role of cats and dogs in asthma and allergy--a systematic review

Studies have reported contradictory effects of cat and dog exposure on allergy, resulting in inconsistent recommendations on animal avoidance. We conducted a systematic review of observational studies published in English from 2000 to January 2009. It shows in this review that the reported exposure-response relationships are contradictory. A total of 17 and 13 birth cohort studies on cat and dog exposure, respectively, are included in the review. Most of the birth cohort studies found that cat or dog exposure in early life had no effect on the development of asthma or wheezing symptoms and dog exposure during infancy was found to protect children from developing sensitization against aeroallergens. A total of 7 and 6 prospective studies in school-age children or adults on cat and dog exposure, respectively, are included in this review and most of these studies suggested an inverse association between cat exposure and asthma and wheezing symptoms. As for cross-sectional studies, 26 and 21 studies on cat and dog exposure, respectively, are included in this review, which cover a broad range of age groups and geographical areas, and reported inconsistent results. The evidence summarised in this systematic review needs to be interpreted with caution, the inconsistent study results may be due to study design, exposure assessment, and avoidance measure. The exposure-response relationships may also alter in geographical areas where the community prevalence of cats and dogs are significantly different. However, as the evidence of the effects of pet keeping on subsequent development of asthma or allergic diseases presented in this review are not overwhelmingly strong, the decision of whether to keep a cat or a dog in the family should be based on arguments other than the concern of developing asthma and allergy.

Allergen tolerance versus the allergic march: the hygiene hypothesis revisited

In addition to genetics, several environmental variables appear to impact allergic risk. Meta-analyses of epidemiologic studies presented in this article demonstrate a correlation between specific ambient exposures (eg, livestock, pets, endotoxin, and unpasteurized milk ingestion) and reduced allergic risk during childhood. Additional laboratory investigations discussed in this review characterized the intrinsic immunostimulatory activities of living environments. Considered together, results of these investigations suggest a novel paradigm by which early-life home exposures to microbial products and other allergen-nonspecific immunostimulants modify allergic risk.

Exposure to animals and the risk of allergic asthma: a population-based cross-sectional study in Finnish and Russian children

BACKGROUND

There is little information on potential differences in animal exposure between Finland and Russia and particularly on the effects of animal exposure on asthma among Russian children. The aim of the study was to compare the pet and farm animal exposures and to assess the relations of pre- and postnatal animal exposures to the occurrence of allergic asthma in Finnish and Russian school children.

METHODS

We conducted a population-based cross-sectional study in neighbour towns on either side of the Finnish-Russian border; Imatra in Finland and Svetogorsk in Russia. The study population consisted of 512 Finnish and 581 Russian school children aged 7-16 years (response rate 79%). Multivariate logistic regression analysis was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI) related to each exposure.

RESULTS

Current indoor exposure to pets was more frequent among school children in Svetogorsk than in Imatra (67.5% vs. 56.0%, P < 0.001). Finnish children were exposed more frequently to dogs, whereas Russian children to cats during childhood and to farm animals during pregnancy and infancy. The risk of self-reported allergic asthma was inversely related to indoor dog keeping ever in Finland (adjusted OR 0.35, 95% CI 0.13, 0.95), whereas in Russia the risk of allergic asthma was increased in relation to combined indoor cat exposure during infancy and currently (4.56, 1.10, 18.91). The risk of asthma was elevated in relation to contact to farm animals during pregnancy (Finland: 1.95, 0.69, 5.50; Russia: 1.90, 0.70, 5.17) and early life (Finland: 2.05, 0.78, 5.40; Russia: 1.21, 0.39, 3.73).

CONCLUSION

Exposure to pets and farm animals during childhood differed significantly between Finland and Russia. Our study provides evidence that early-life exposure to cats increases the risk of asthma whereas exposure to dogs is protective. Our findings suggest that intermittent fetal and early-life exposure to farm animals increases the risk of allergic asthma in urban children visiting farms.

How strong is the evidence that immunotherapy in children prevents the progression of allergy and asthma?

PURPOSE OF REVIEW

The purpose of this review is to describe the scientific evidence that specific immunotherapy can prevent the development of asthma in patients suffering from rhinoconjunctivitis as well as reduce the number of new allergies developing.

RECENT FINDINGS

Proposed strategies for the prevention of the development of allergic rhinoconjunctivitis and asthma include allergen avoidance, pharmacological treatment (antihistamines and steroids) and specific immunotherapy. Long-term follow-up on immunotherapy studies demonstrates that specific immunotherapy for 3 years shows persistent long-term effects on clinical symptoms after termination of treatment and long-term, preventive effects on later development of asthma in children with seasonal rhinoconjunctivitis. It is so far the only treatment for allergic diseases that has been shown to be able to prevent worsening of disease and development of asthma. Also, specific immunotherapy seems to reduce the development of new allergic sensitivities as measured by the skin prick test as well as specific IgE measurements.

SUMMARY

Specific immunotherapy is the only treatment that interferes with the basic pathophysiological mechanisms of the allergic disease and thereby carries the potential for changes in the long-term prognosis of respiratory allergy. Specific immunotherapy should be recognized not only as first-line therapeutic treatment for allergic rhinoconjunctivitis, but also as secondary preventive treatment for respiratory allergic diseases.

Environmental exposure to allergens of different dog breeds and relevance in allergological diagnostics

In our environment, dogs are a relevant source of allergens, but diagnosing dog-related allergies may present difficulties, as in diagnostic tests with commercial dog allergens, some patients show only slight positive or negative results, even though they suffer from dog-related symptoms. Occasionally, allergy tests with extracts of dog hair belonging to patients' dogs or from dogs of the same breed were found to yield more reliable results, possibly due to breed-specific allergen components. The purpose of this study was to determine breed-specific differences or possibly hypo- or hyperallergenic dog breeds. The dog allergen content and protein patterns of different commercial and self-prepared dog allergen extracts were compared. Protein extracts were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and stained with silver. The major allergen Can f 1 was quantified using the commercially available enzyme-linked immunosorbent assay (ELISA) technique. The majority of the bands in the self-prepared extracts of different breeds had a molecular mass lower than 30 kD. Notably, the self-prepared extracts of hair of common breeds showed distinct protein bands with a molecular mass lower than 14 kD, which the commercial extracts did not. With regard to Can f 1 content, a marked variability occurred. Factors related to individual dogs seem to influence the allergenicity more than breed or gender. This is the first report to describe allergens with low molecular mass that are absent in extracts of commercial test kits. Consequently, skin tests with self-prepared dog allergen extracts need to be performed in case of inconsistent test results with commercial extracts.

A prospective study of allergy development in 158 children and 128 adults with new extensive exposure to furred animals

BACKGROUND

There is still controversy over whether exposure to furred animals increases or decreases the risk of developing sensitization and allergic symptoms to such animals, and there is a need for further knowledge on this subject.

OBJECTIVE

The aim of this study was to follow allergy development in relation to new extensive exposure to furred animals in adults and children.

METHODS

A total of 286 individuals, 128 parents and 158 children, were recruited from 68 families who intended to buy a dog or a cat, or where one child of the family intended to start riding a horse. Subjects were examined before the new allergen exposure and once a year thereafter for 5 years, in all at six occasions, and they also completed questionnaires covering allergy symptoms. Serum IgE antibodies to cat, dog and horse were determined each year, and fur allergens from beds and living rooms were analysed.

RESULTS

Two-hundred and fifty-six study subjects remained for evaluation, 37 of whom showed signs of allergic sensitization at the start of the study. Four children (11%) in this pre-sensitized group developed IgE antibodies to their new animal and six (16%) to another animal. Among the 219 participants who were not sensitized when entering the study, one male adult (0.4%) developed a sensitization to his new animal, and nobody developed sensitization to other animals. Pre-sensitized individuals had significantly more allergic symptoms at the study start, but the symptom scores did not change over time.

CONCLUSIONS

When the first year of a human's life has passed, we have no strong evidence to recommend avoidance of a domestic animal in order to prevent new allergy development, even if there are known allergies in the family or if the individual is sensitized and has allergic symptoms to another allergen. Five years exposure to new fur allergens does not seem to influence sensitization to these animals in either sensitized or non-sensitized children and adults.

Prevalence and host determinants of occupational bronchial asthma in animal shelter workers

OBJECTIVE

We examined the risk factors for the development of airway allergy in animal shelter workers.

METHODS

The study population comprised 88 animal shelter workers occupationally exposed to cats and dogs. They responded to a questionnaire concerning the history of exposure to animal allergens and job characteristics and were subjected to skin prick test (SPT) to common and occupational allergens (cat and dog), and determination of total serum IgE level and specific IgE. In addition, SPT with rat and mouse allergens were performed. Bronchial hyperreactivity and peak expiratory flow rate were measured at work and off work only in workers with work-related symptoms suggestive of occupational asthma (OA).

RESULTS

The prevalence of OA was 9.1%. Sensitization to dog allergens was higher than to cats. The multivariate logistic regression analysis revealed a significant role of positive family history of atopy and having a dog as pet in the past for the development of occupational airway allergy (OR 5.9; 95% CI 1.76, 20.00; P = 0.003; OR 6.47; 95% CI 1.90, 22.02; P = 0.002, respectively). In the multivariate logistic regression analysis, the risk for developing OA was most clearly associated with growing up in the country (OR 7.59; 95% CI 1.25, 45.9; P = 0.025).

CONCLUSIONS

Allergic disease is a serious occupational health concern for subjects who have occupational contact with cats and dogs.

Evaluation of the relationship between cockroach sensitivity and house-dust-mite sensitivity in Turkish asthmatic patients

Exposure to cockroach has been identified as an important source of indoor allergens in patients with asthma and allergic rhinitis. We evaluated the relationship between cockroach sensitivity and other allergens in patients with asthma. A total of 114 patients, defined asthma according to GINA, were enrolled in this study. A questionnaire including age, sex, duration of asthma, history of cockroach presence at home, and total IgE, blood eosinophil count, pulmonary function tests, standard skin prick test additional cockroach and shrimp allergen were performed. There were 84 (73.7%) female and 30 (26.3%) male patients with a mean age of 38.1+10.1 years. The average duration of asthma was 7.7+7.2 years. Sixty five (57%) patients were determined atopic and 49 (43%) nonatopic. Pollen allergen was the most common allergen in 59 (51.8%) patients with asthma, and second common allergen was mite allergen in 43 (37.7%) patients. Cockroach sensitivity were detected in 23 (20.2%) of 114 all asthmatics and 23 (35%) of atopic asthmatics. High rates of house-dust-mite allergy (73.9%) was determined in patients with cockroach sensitivity (P<0.05), while we found no relationship with other allergens. There was no difference for cockroach sensitivity between rural and urban population. Cockroach sensitivity was more common in mild bronchial asthmatics and a female predominance was observed. In addition, there was no association between shrimp and cockroach sensitivity. As a result, a high rate of cockroach sensitivity alone or with mite sensitivity was seen in patients with bronchial asthma in Turkish population. Because of cross-reactivity between mites and cockroach, cockroach sensitivity should be investigated in patients with house-dust-mite allergy. In addition, a high rate of cockroach sensitivity, in terms of IgE sensitization, may be important for the development of new sensitizations.

High-dose allergen exposure leads to tolerance

Reports of decreased sensitization to cat allergen (Fel d 1) among individuals living with a cat or subjects exposed to high-dose cat allergen may be explained by the development of a form of high-dose tolerance resulting from natural exposure to an inhalant allergen. Although the epidemiological data regarding the relationship between exposure and sensitization to Fel d 1 are conflicting, the ability for high-dose Fel d 1 to induce a characteristic nonallergic immune response with a distinctive serum antibody profile has been established. Definition of this modified T-helper (Th)2 response to cat allergen, coupled with the renewed interest in regulatory T cells within the immunology field, has provided an avenue for exploring the mechanism by which IgE antibody-mediated responses are controlled. There is mounting evidence to suggest that the modified Th2 response is a variation of the allergic response and that the modified Th2-allergic axis is influenced by allergen dose and genetics. This article discusses putative immune mechanisms of tolerance within the context of an allergen-specific system. The relevance of high-dose allergen exposure and alternate factors such as endotoxin to the development of tolerance is considered. Fel d 1 exhibits unique molecular and immunological characteristics that may contribute to its tolerogenic properties. Major T-cell epitopes of Fel d 1 that preferentially induce regulatory factors have been defined. Furthermore, high-titer IgE antibody responses associated with atopic dermatitis are characterized by a defect in the T-cell repertoire that is specific to these epitopes. Identification of Fel d 1 epitopes that induce interleukin-10 may provide new targets for treatment.

Dog factor differences in Can f 1 allergen production

BACKGROUND

The clinical importance of dog allergy is well known, but it is unknown if all types of dogs represent the same risk for allergic patients. The purpose of this work was to evaluate among 288 healthy dogs if the levels of Can f 1 on fur vary between breeds (German Shepherd, Pyrenean Shepherd, Poodle, Cocker spaniel, Spaniel, Griffon, Labrador retriever and Yorkshire terrier), gender, hormonal status, hair length, and according to the presence of seborrhea.

METHODS

Each dog was shaved in a limited area and Can f 1 concentrations were measured in mug/g fur by ELISA. The results (geometric mean values and 95% confidence intervals) were analyzed using analysis of variance and with nonparametric tests.

RESULTS

A wide variability in Can f 1 levels was found between dog breeds, from Labradors [1.99 (0.03-129.91)] to Yorkshires [16.72 (3.67-76.16)] and Poodles [17.04 (2.79-103.94)] but only the Labrador levels were significantly different from each other breed. Males produced more Can f 1 than females, 11.75 (1.27-108.40) vs 8.89 (0.91-86.39). No difference was found according to hair length or hormonal status. The seborrheic status highly (P = 0.0019) influenced the presence of Can f 1 on hair: 16.66 (1.59-173.96) vs 9.40 (1.03-85.70).

CONCLUSION

Breeds (Labrador retriever), sex and seborrhea seem to influence the levels of Can f 1 on fur.

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.

Ontogeny of the Allergic Inflammatory Response

The ability to produce allergic responses begins early in fetal life along with the development of other elements of the immune system. Among the most interesting questions related to the development of allergic disease are whether the fetus in utero commonly is exposed to sufficient allergen to induce IgE production and how much the mother's immune responses affect the developing fetal immune system. After birth, it seems that many factors, including the frequency and severity of infections and the timing and intensity of allergen and animal exposures, continue to influence immune development.

Respiratory symptoms and hamsters or other pets: a large-sized population survey in Saitama Prefecture

BACKGROUND: Keeping hamsters as pets has been increasing markedly. Clinical reports have suggested that hamster or other pet ownership is associated with respiratory symptoms. However, this association has not been fully investigated by population-based studies in Japan. The aim of the present study was to investigate the relationship between hamster ownership and respiratory symptoms by using a questionnaire.

METHODS: During the period of August 1 to 20, 2002, we conducted a cross-sectional survey in Saitama Prefecture, which has a total population of approximately 7 million. First, we selected, proportionally to the population size, 100 areas from 5 administration districts of Saitama Prefecture. From each area, 30 households were chosen: 15 living in detached houses and 15 living in other types of dwelling, such as apartment houses. In this way, 2 groups based on type of dwelling (detached house versus other types) could be studied. A lay away plan was carried out. For the survey, 2 questionnaires were developed. One was a questionnaire dealing with household conditions, including pet keeping. The other sought details regarding individual health and lifestyle conditions. The questionnaire dealing with respiratory symptoms asked “whether the respondents had experienced respiratory symptoms (wheezing and/or breathlessness and/or bad cough) in the last 12 months.”

RESULTS: The response rate was 78.9%. There were 7,395 respondents in 2,368 households. There was no association between either dog or cat ownership and respiratory symptoms. In contrast, hamsters kept in the home were positively associated with respiratory symptoms. In a multivariate logistic regression analysis, hamster ownership increased the odds ratio for respiratory symptoms (odds ratio: 1.57; 95% confidence interval: 1.18-2.10).

CONCLUSION: This large size population-survey indicated that hamster ownership is associated with respiratory symptoms.

Remission of allergic rhinitis: An 8-year observational study

BACKGROUND

Allergic rhinitis (AR) and sensitization are considered chronic conditions. However, few studies have reported remission rates in adults.

OBJECTIVE

We sought to estimate the incidence of remission of AR during an 8-year period.

METHODS

Participants in a population-based study of 15- to 69-year-old patients in 1990 were invited to a follow-up in 1998. Questionnaires on respiratory symptoms and serum for specific IgE (s-IgE) analyses were collected at both visits in 734 subjects (69% of those invited). Pollen AR was defined as rhinitis symptoms on pollen exposure within the last 12 months and s-IgE levels of class 2 or greater against pollen (birch, grass, or mugwort). This was similar for AR to animals (cat or dog) or house dust mites (HDMs). Remission of AR was defined as AR at baseline but no rhinitis symptoms at follow-up and sensitization (s-IgE level class > or =2 at baseline and class <2 at follow-up).

RESULTS

Remission of AR occurred in 12% (pollen AR), 19% (animal AR), and 38% (HDM AR; overall, 17%) and was predicted by low s-IgE levels. Age, sex, asthma, atopic predisposition, age at AR onset, and AR duration had no predictive value. A decrease in s-IgE level was observed in only 22% of remitting subjects yet was seen significantly more often than in nonremitting subjects (7.4%). Remission of sensitization occurred in 6% (HDM) to 11% (pollen-furry animal) and was predicted on the basis of low s-IgE levels (class 2) at baseline.

CONCLUSION

Remission of AR symptoms was relatively infrequent, and remission of both symptoms and IgE sensitization was rare. The results underline the chronic nature of AR in adulthood.

Cutaneous and serological responses to cat allergen in adults exposed or not to cats

BACKGROUND

The relationship between pet ownership and the risk of developing respiratory allergic sensitization to pet allergens is still controversial.

OBJECTIVE

To determine the degree of cutaneous immediate hypersensitivity and the levels of specific IgE and IgG4 antibodies to cat allergen in cat sensitized patients directly or indirectly exposed to this animal.

METHODS

We studied 112 adolescents and adults sensitized to cat allergens (43 with and 69 without a cat at home). There were also 52 control subjects, 27 atopic non-sensitized to cat and 25 non-atopic. The degree of immediate hypersensitivity was assessed by using, in duplicate, skin prick test with four five-fold dilutions of cat hair allergen extract with the content of its major allergen Fel d 1 quantified in micrograms plus positive (10 mg/ml histamine chlorhydrate) and negative (saline solution) controls. The resulting wheal areas were analysed by means of Parallel Line Assay. A blood sample was collected from every patient and control subjects for the evaluation of serological cat specific IgE and IgG4 antibodies.

RESULTS

Patients with cat at home had a lower cutaneous response than patients without this pet. The difference in the skin sensitivity was estimated in 3.4 times (P<0.01). There was no statistical difference between the levels of cat specific IgE antibodies in the two groups of patients (P=0.065). The levels of Fel d 1 specific IgG4 antibodies showed a statistically significant association with the presence of cat at home, with higher levels in patients owing cat at home than in patients without this pet (P<0.001).

CONCLUSION

The results of this study demonstrate that direct cat exposure in adolescents and adults with respiratory allergy is associated with a lower cutaneous response to cat allergenic extract, assessed by SPT and compared with indirect exposure. In patients with cat at home mean levels of specific IgE are statistically comparable whereas the levels of IgG4 are higher in comparison with subjects not exposed to cats. The role of indirect exposure to cat allergens in airways sensitization also in adults is emphasized. Moreover, patients with cat at home show a cutaneous and serological sensitization to cat allergen not higher in comparison with subjects not exposed to cats.

Prognostic value of asymptomatic skin sensitization to aeroallergens

PURPOSE OF REVIEW

Asymptomatic skin sensitization to aeroallergens is frequently encountered in epidemiological studies and in everyday clinical life. Correct management of the condition is essential to avoid both progression into allergic disease and unnecessary intervention. Understanding immunological mechanisms in asymptomatic skin sensitization might provide new insights into the natural history and treatment of respiratory allergy.

RECENT FINDINGS

Research on asymptomatic skin sensitization is rare, and the present review unites previous studies with recent findings. It is a common condition affecting 8-30% of the population when using a local standard panel of aeroallergens. Clinically, immediate but not late-phase reactions are induced by allergen challenge. Absent eosinophil stimulation and migration and low IL-5 levels appear to be sentinel mechanisms. Prospective studies show that 30-60% become allergic, depending on allergens and follow-up period. No prospective intervention studies have been performed; however, allergen avoidance seems efficacious in reducing allergy development to occupational and domestic allergens. Asymptomatic skin sensitization due to an erroneously positive skin test must be ruled out before allergen avoidance measures are initiated.

SUMMARY

Surprisingly few papers exist on asymptomatic skin sensitization epidemiology and immunology, despite the intriguing question as to why symptoms do not develop in IgE-sensitized patients. It is a common condition and a risk factor for later development of respiratory allergic disease. Cross-sectional intervention studies suggest that allergy development is reduced by allergen avoidance. Immunologically, control of eosinophil stimulation and migration seems to be pivotal. How this control is maintained remains to be elucidated.