Exposure to indoor allergens and development of allergy

House dust contains several indoor allergens which can elicit hypersensitivity and various atopic symptoms, especially in childhood. This review article focusses on house dust mite hypersensitivity to one of the most important species, Dermatophagoides , as a model. A clear dose-response relationship has been demonstrated between house dust mite allergen exposure in mattress dust samples and sensitization, i.e. serum IgE to Dermatophagoides and positive histamine release from basophil leukocytes to one of the major allergens from Dermatophagoides pteronyssinus, Der p I. 2 μg major allergen of Dermatophagoides /g of dust and 8 μg major allergen of cat/g of dust have been suggested to be threshold concentrations above which the risk of sensitization in genetically predisposed atopic children is significantly increased. Epidemiological studies showed house dust mite allergens to be one of the most important risk factors in the development of atopic airway disease. A relation between age at onset of the first wheezing episode and house dust mite allergen exposure at the age of 1 year has been observed. There are various factors influencing house dust mite growth, and many studies have been performed to reduce house dust mite allergen exposure. Until now, none of the approaches appeared to have achieved sufficient mite and mite allergen reduction.     

Seasonal variations in house dust mite allergens--significance for children with allergy

Allergenic proteins of the house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae and their major allergens Der p I and Der f I are one of the most significant environmental factors which may facilitate sensitization and allergic airway disease in childhood. In order to measure seasonal variations of mite allergen exposure, we collected mattress dust samples monthly in 13 homes over a period of 1 year. Der p I and Der f I were determined with a sandwich type ELISA. Mite allergen levels were significantly lower from January-June than from July-December (p less than 0.05) which was mostly due to Der p I variations. Only in 6 of the studied homes seasonal variations in mite allergen concentrations according to seasonal variations in outdoor humidity could be observed. In 7 homes mite allergen exposure stayed constant and seemed to depend only on indoor climate factors.     

Study on the Prevention of Allergy in Children in Europe (SPACE): Allergic sensitization at 1 year of age in a controlled trial of allergen avoidance from birth

Several studies have demonstrated that early intervention may modulate the natural course of atopic disease. The objective of this study was to prevent sensitization to house dust mite and food allergens, as well as development of atopic symptoms, during infancy. To achieve this we employed the combination of an educational package with the use of mite allergen-impermeable mattress encasings. A multi-center European, population-based, randomized controlled study of children at increased atopic risk [study on the prevention of Allergy in Children in Europe (SPACE)] was performed in five countries (Austria, Germany, Greece, Great Britain, Lithuania) and included three cohorts of schoolchildren, toddlers and newborns. We report on the newborn cohort. A total of 696 newborns were included in Austria, Great Britain and Germany. Inclusion criteria were a positive history of parental allergy and a positive skin-prick test or specific immunoglobulin E (IgE) of ≥ 1.43 kU/l against at least one out of a panel of common aeroallergens in one or both parents. At 1 year of age the overall sensitization rate against the tested allergens [dust mite allergens: Dermatophagoides pteronyssinus and D. farinae ( Der p and Der f, respectively)] and food allergens (egg, milk) in the prophylactic group was 6.21% vs. 10.67% in the control group. The prevalence of sensitization against Der p was 1.86% in the prophylactic group vs. 5% in the control group. In conclusion, we demonstrated, in a group of newborns at risk for atopic diseases, that the sensitization rate to a panel of aero- and food allergens could be effectively decreased through the use of impermeable mattress encasings and the implementation of preventive measures that were easy to perform.     

Randomized trial to prevent sensitization to mite allergens in toddlers and preschoolers by allergen reduction and education: one-year results

OBJECTIVE: To evaluate the effectiveness of prevention measures against dust mite sensitization. DESIGN: European (England, Germany, Greece, Lithuania) multicenter prospective single-blind randomized control trial with a follow-up of 12 months. PARTICIPANTS: Toddlers and preschoolers, with at least 1 parent with atopic symptoms and sensitization, who initially were not sensitized to mite allergens. INTERVENTIONS: A combination of education and a simple preventive measure (mattress encasement) to reduce mite allergen exposure. SETTING: Community-based study. MAIN OUTCOME MEASURES: Sensitization to mite allergens (skin-prick test or specific immunoglobulin E). RESULTS: Of 636 children (mean age, 3.1 years) included in the study, 566 (89%) participated in the first-year follow-up. The incidence of sensitization to mite allergens was 10 (3%) of 330 in the intervention vs 20 (6.5%) of 306 in the control arm, including loss of follow-up (intention-to-treat principle). Allergic symptoms were more common in sensitized than in nonsensitized children and so was the prevalence of physician-diagnosed asthma, eczema, and food allergy. CONCLUSIONS: This simple, harmless, and inexpensive measure can be used in toddlers and preschoolers of parents with atopic disorders to reduce sensitization to mite allergens. With regard to clinical manifestations of atopy, follow-up studies are needed to determine the effectiveness of the intervention.     

Study on the Prevention of Allergy in Children in Europe (SPACE): Allergic sensitization in children at 1 year of age in a controlled trial of allergen avoidance from birth

Several studies have demonstrated that early intervention may modulate the natural course of atopic disease. Our objective was to prevent sensitization to house-dust mite and food allergens, as well as the development of atopic symptoms during infancy, by the combination of an educational package and the use of mite allergen-impermeable mattress encasings. A multicentre European, population-based, randomized, controlled study of children at increased atopic risk [Study on the Prevention of Allergy in Children in Europe (SPACE)] was performed in five countries (Austria, Germany, Greece, the UK, and Lithuania), and included three cohorts – schoolchildren, toddlers, and newborns. We report on the newborn cohort. A total of 696 newborns were included from Austria, the UK, and Germany. Inclusion criteria were: a positive history of parental allergy; and a positive skin-prick test or specific immunoglobulin E (IgE) (IgE ≥ 1.43 kU/L) against at least one out of a panel of common aeroallergens in one or both parents. At 1 year of age, the overall sensitization rate against the tested allergens [dust-mite allergens: Dermatophagoides pteronyssinus and Dermatophagoides farinae ( Der  p and Der  f)] and food allergens (egg, milk) in the prophylactic group was 6.21% vs. 10.67% in the control group. The prevalence of sensitization against Der  p was 1.86% in the prophylactic group vs. 5% in the control group. In conclusion, we were able to demonstrate, in a group of newborns at risk for atopic diseases, that the sensitization rate to a panel of aero- and food allergens could be effectively decreased through the use of impermeable mattress encasings and the implementation of easy-to-perform preventive measures.     

Atopy patch testing in children with asthma and rhinitis symptoms allergic to house dust mite

The atopy patch test (APT) is generally used to assess immunoglobulin E (IgE) mediated sensitization to allergens in patients with atopic dermatitis, but its diagnostic role in children with respiratory allergy is still controversial. The aim of the study was to evaluate APT with house dust mite (HDM) in children with asthma and rhinitis symptoms allergic to HDM and its relevance to skin prick test (SPT) diameters and specific IgE levels. The study population consisted of 33 children, aged 8-16 yr (median: 12 yr) with asthma and 30 children with allergic rhinitis in the same age range (median: 11 yr). All patients had positive SPT results and high serum specific IgE levels for Dermatophagoides pteronyssinus APT was performed on back skin of all patients with 200 index of reactivity (IR)/ml of D. pteronyssinus allergen extracts in petrolatum (Stallerpatch) and evaluated at 72 h. Of 63 patients, 16 (25%) showed a positive patch test result. APT with HDM showed 30% (10/33) positivity among the patients with asthma and 20% (6/30) positivity among the patients with allergic rhinitis. APT presented no significant correlation with age, SPT diameter, serum total and specific IgE levels for D. pteronyssinus, nasal provocation test or pulmonary function test results. Patch testing with HDM may partly identify mite sensitive children with respiratory allergy. Positive APT results may imply that delayed hypersensitivity reactions play a role in children with asthma and rhinitis allergic to HDM.     

Exposure to a high concentration of mite allergen in early infancy is a risk factor for developing atopic dermatitis: A 3-year follow-up study

The cause of allergy is multi-factorial, and the development of an allergic disease seems to be the result of an interaction between genetic and environmental factors. The goal for preventing the development of allergic diseases is to avoid sensitization to allergens. The aim of this work was to study whether or not exposure to environmental allergens early in infancy would influence the occurence of various allergic diseases in later life. On an annual basis, a total of 931 healthy newborns were followed-up until they reached 3 years of age. The occurence of allergic diseases was recorded by trained medical students during visits. Measurement of Dermatophagoides pteronyssinus (Der p 1) concentration in house dust was performed when each baby was 18 and 36 months old. Total and specific immunoglobulin E (IgE) antibodies against Der p 1, cow's milk, and egg white were evaluated at birth and at 18 months of age. The following results were obtained: at 3 years of age, 10.4% had bronchial asthma (BA), 21.4% atopic dermatitis (AD), 7.0% urticaria, and 46.8% had experienced wheezing; higher family allergy scores led to a higher incidence of AD (p=0.0012); exposure to a mite allergen concentration of 1 µg/g of dust may be associated with a higher incidence of AD (p=0.0156); the presence of Der p 1 IgE antibody at 18 months of age was associated with a higher incidence of BA (p=0.0001); and children sensitized to egg whites at 18 months of age had an increased risk of developing AD at 3 years of age (p=0.0187). Hence, early exposure to mite allergen is a risk factor for the development of atopic dermatitis, but seems not to be related to the development of bronchial asthma. Early sensitization to egg whites increases the risk of developing AD. The early detection of serum Der p 1 IgE antibody is associated with a higher incidence of bronchial asthma.     

The effect of high-efficiency and standard vacuum-cleaners on mite, cat and dog allergen levels and clinical progress

The major triggers for allergic asthma are exposure to allergens of the house dust mite, Dermatophagoides pteronyssinus , and of pets. Unfortunately studies of techniques designed to reduce house dust mite and pet allergens have had mixed results. However, new so-called 'improved' products continue to appear on the market and require subjective evaluation. The homes of 60 house dust mite-allergic patients were studied to compare the effects of high-efficiency and standard vacuum-cleaners on allergen concentration. Der p 1 (house dust mite), Fel d 1 (cat) and Can f 1 (dog) allergens were measured in four separate locations in each home. Clinical analysis was by lung function, bronchodilator usage and histamine challenge techniques. There was a significant reduction in Fel d 1 (ng/m²) in dust samples from the living-room carpet (p = 0.046), bedroom carpet (p = 0.003) and mattress (p = 0.013) and living-room sofa (p = 0.005) after 12 months of using the high-efficiency cleaners, but only in the mattress sample using the standard cleaners (p = 0.014). Can f 1 (ng/g dust) was reduced in the mattress sample after using the high-efficiency vacuum-cleaners (p = 0.028), but not at other sites. Der p 1 levels were not significantly changed over this period. Clinically, patients in the high-efficiency group showed improvements in peak expiratory flow rate (PEFR) (p = 0.004), FEV₁ (p = 0.026) and bronchodilator usage (p = 0.005) after 12 months. When the cat-sensitive patients were analyzed separately, improvements in histamine PC₂₀ (p = 0.039) were also seen. Reducing Fel d 1 concentrations, in the absence of any change in Der p 1 concentrations, can produce significant improvements in the lung function of atopic, asthmatic patients. This effect was primarily achieved in those patients with cat sensitivity, but who did not possess a cat themselves.     

Sensitization to house dust mites: importance and possibilities of allergen elimination]

House-dust mite allergy (Dermatophagoides pteronissinus and Dermatophagoides farinae) is an important causative factor for allergic asthma or rhinitis in children. There is a clear relationship between the degree of allergen exposure and the subsequent development of asthma or the risk of sensitisation. It is therefore useful to know how intensive a patient is exposed to house-dust allergen. This can be managed either by counting all mites in the dust, by measuring of the content of Der p I and Der f I (major antigens of the two mites) per gram dust or using the Acarex test. These methods are also suitable for the control of sanitation measurements, e.g. avoidance of all dust sources in the bedroom and living-room, use of suitable materials for bedding, application of acaricide products and covering mattresses with polyurethane-coated materials.     

Prenatal exposure to mite and pet allergens and total serum IgE at birth in high-risk children

To examine the relationship between prenatal exposure to mite, cat and dog allergens and total serum IgE at birth in newborns at high risk of asthma. In the homes of 221 newborns with at least one first-degree relative with asthma, concentrations (ng/g dust) of allergens of house dust mite (mite), cat and dog were measured at the fourth to sixth month of pregnancy in dust samples from the maternal mattress and living room. At day 3-5 after birth, total IgE was measured in capillary heel blood. A total number of 174 blood samples were available (11 mothers refused newborn's blood sampling, and in 36 cases the blood sample was too small for analysis). In 24% of the newborns, total IgE was elevated (cut-off value 0.5 IU/ml). A significant dose response relationship was found between increasing mite allergen levels [divided in quartiles ng/g dust (qrt)] and the percentage of elevated IgE: first qrt (0-85 ng/g) 13%; second qrt (86-381) 19%; third qrt (382-2371) 26%; fourth qrt (> or =2372) 42%, respectively, p=0.01. This relationship remained significant after adjusting for passive smoking, maternal and paternal mite allergy, socio-demographic factors, birth characteristics and (breast) feeding practice in the first week of life. In high-risk newborns, prenatal exposure to mite allergens, but not to cat and dog allergens from dust of the living room and of the maternal mattress was associated with total serum IgE at birth.     

Allergens and asthma.

This article presents the studies that show that asthma in children is strongly associated with sensitization to dust mite and other indoor allergens. In addition, the recent evidence that this association reflects a causal relationship between allergen exposure and asthma is reviewed. The relevance of quantitative measurements of the major indoor allergens (dust mite, cockroach, and cat) in the houses of children with asthma is discussed. Finally, the increasing evidence that avoidance measures can be an effective treatment for asthma is considered together with the details about avoidance protocol for dust mite and cat allergen.     

Childhood asthma and exposure to indoor allergens: lowmite levels are associated with sensitivity

The prevalence and level of sensitivity to indoor allergens were studied in relation to current exposure at home in 124 children with perennial asthma living in three climatic zones of Sweden. The house dust mite (HDM) allergen levels were higher in the South than in the North (p < 0.001), while cat and dog allergen levels tended to be higher in the North than the South (n. s.). Thirty-four percent of the children were sensitive to the HDM Dermatophagoides pteronyssinus , as determined by IgE antibodies in vitro, 27% were sensitive to D. farinae , 57% to cat and 55% to dog. Sensitivity to HDM was significantly more prevalent in Southern, than in Central and Northern Sweden (p=0.001) where the children were more often sensitive to pets (cat p=0.005, dog p= 0.002). A significant association between the concentration of Der p I and Derf I in the house dust and both the prevalence of sensitivity to HDM and the IgE antibody levels against mites was found even at concentrations well below the commonly suggested risk level for sensitisation of 2 μg/g dust. No relationship was found between pet allergen concentration in the home dust and sensitivity to pets, possibly because of exposure outside home, e. g. in schools and meeting places for leisure activities. Similarly, there was no consistent association between the level of mite or pet allergen exposure at home and asthma severity as judged by symptom and medication score. The study indicates that there is no threshold value for sensitisation to mite allergens in asthmatic children, and therefore, dust allergen levels at home should be kept as low as possible in homes of children at risk for asthma.     

Prenatal exposure to house dust mite allergen (Der p 1), cord blood T cell phenotype and cytokine production and atopic dermatitis during the first year of life

This study investigated the influence of prenatal exposure to house dust mite (HDM, D. pteronyssinus) on interleukin (IL)-2, interferon-gamma (IFN-gamma) and IL-4 producing CD4(+) and CD8(+) T lymphocytes in cord blood as well as on the development of sensitization and occurrence of atopic dermatitis (AD) as the first symptom of allergy during the first year of life. Dust samples (n = 22) were collected by vacuum cleaning the maternal mattress during early to mid-pregnancy. In these samples, the amount of the major HDM antigen (Der p 1) was assessed by a sensitive enzyme-linked immunosorbent assay technique (detection limit 0.004 microg/g dust). Flow cytometry was used to determine cord blood lymphocyte subtypes and to quantify the intracellular amounts of IL-2, IFN-gamma and IL-4 produced by cord blood CD4(+) helper and CD8(+) cytotoxic T lymphocytes, both spontaneously and after stimulation with phorbol-12-mirystate-13-acetate and ionomycin. Children were followed for 1 yr for the presence of symptoms associated with allergy. In addition, at the age of 1 yr specific IgE to different classical inhalant and food allergens was measured. Higher prenatal exposure to Der p 1 (>0.2 microg/g dust) was associated with a significant lower percentage of IFN-gamma producing stimulated CD4(+) T lymphocytes, compared with lower prenatal Der p 1 exposure (p = 0.03). The presence of AD during the first year of life (n = 9) was associated with an increased number of naive CD4(+) CD45RA(+) lymphocytes (p = 0.03), with an increased spontaneous IL-4 production by CD8(+) lymphocytes (p = 0.04) and with a decreased percentage of IFN-gamma producing stimulated CD4(+) lymphocytes (p = 0.04). Furthermore, exposure to HDM during pregnancy tended to be higher in mothers of children with AD during the first year of life when compared with those without AD (p = 0.08). This study shows that the level of prenatal exposure to Der p 1 influences the immune profile of cord blood T lymphocytes and the clinical outcome in early life. Therefore, the prenatal environment must be regarded as a possible early risk factors for allergic diseases in children.     

Asthma attributable to atopy: does it depend on the allergen supply?

The use of the population attributable fraction (PAF) of asthma owing to atopy has not been widely used in epidemiological studies on childhood asthma, especially to compare regions of the same country. The present study includes 1039 children from Cartagena, Spain (Mediterranean coast) and 663 from Madrid (centre of Spanish plateau) using the ISAAC phase II methodology (questionnaire and prick test to the most common allergens). While there were no differences in asthma symptoms between school children (aged 10-11 yr) from Madrid and Cartagena, atopy to any allergen was significantly higher in those from Madrid (40.9% vs. 29.3%, respectively, p < 0.0001). However, children from Madrid were mainly positive to pollen allergy whereas those from Cartagena were positive for mite allergy. PAF of all the different asthma symptoms owing to atopy (any positive skin test) and PAF of current wheezing owing to a more severe atopy (three positive wheals) were higher in children from Cartagena than those from Madrid (45.5% vs. 28.6% and 14.2% vs. 6.2%, respectively). Per cent of previous year wheezing attributable to atopy to specific allergens varied among those cities and was higher for D. pteronissinus, D. farinae, cat, and olive tree in children from Cartagena, and--conversely--higher for mixed grasses, mixed trees and Alternaria in those from Madrid. All of these differences remained significant even after adjusting for risk factors. PAF for asthma owing to atopy could be very different within the same country, probably depending on the allergen supply which may depend on environmental factors such as the climate.     

Mite allergy, clinical atopy, and restriction by HLA class II immune response genes

From a community-based study cohort of 1812 elementary schoolchildren we selected 129 unrelated participants to investigate the relevance of HLA-class II molecules (DPB, DQB, and DRB) to the regulation of immune response to the mite allergen Der p 1 and to clinical atopic disorders. On the basis of skin prick test results validated by measurement of specific IgE, individuals were selected and divided into three groups: group I (n = 20), controls without detectable specific IgE to common inhalant allergens; group II (n = 22), children sensitized only to non-mite allergens; group III (n = 85), children sensitized to Der p 1. Clinical history of asthma, eczema, and hay fever was ascertained using standardized questionnaires. In total, 43 different HLA class II alleles (DPB, n = 19; DQB, n = 14; and DRB, n = 10) were determined by sequence-specific oligonucleotide typing with PCR-amplified DNA. We were not able to demonstrate significant differences in gene frequencies of any HLA class II allele between the group of mite-sensitized children and one of the other two groups. However, the presence of certain DRB- and DPB-haplotypes (DRB *0100/*0300/*1100 and DPB *0201/*0401) was significantly associated (p < 0.01) with a history of asthma, hay fever, and atopy (defined as a history of asthma and/or hay fever and/or eczema). Other haplotypes, including DQB *0303/*0503, DRB *0200/*0700, and DPB 0402 were negatively associated with a history of eczema, hay fever, and atopy (p < 0.01). Thus, our findings do not suggest a relevance of HLA-class II molecules to mite allergy; however, some HLA class n haplotypes appear to be predictive of the incidence of atopic disorders.     

Mites in dust samples from mattress surfaces from single beds or cribs in the south Brazilian city of Londrina

The aim of this study was to investigate the mite fauna in mattresses dust samples from cribs or beds in the south Brazilian city of Londrina, State of Parana. A total of 133 dust samples from upper and lower mattress surfaces, and bed frames were aspirated once from 38 dwellings (18 cribs and 21 beds), and one day nursery (six cribs). A total of 758 mite bodies were counted in slides: 233 (30.7%) from cribs and 525 (69.3%) from beds (p<0.001). House dust mites--mainly Dermatophagoides pteronyssinus, represented 72% and 84% of total mite count in crib and bed dust samples, respectively. The mean HDM body concentration in crib or bed slides were, respectively, 289.9+/-136.7 and 875.0+/-183.6 mites/g. Statistical analysis showed a significantly higher mite bodies count on lower mattress surface compared with upper surface in bed samples only (p=0.025). Data herein show that cribs like mattress have sufficient mite bodies to cause sensitization to humans. The use of mattress covers for cribs and beds should be encouraged in order to avoid allergens exposure.     

Risk factors for asthma in inner city children.

Inner city children have the highest prevalence and the highest mortality rates for asthma in the United States. The purpose of this study was to evaluate sensitization and exposure to common indoor allergens among children aged 3 years to 15 years seen for treatment of asthma at Grady Memorial Hospital, Atlanta, Ga. Eighty children in this study were enrolled in the emergency department and 64 in hospital clinics. Dust from 57 homes, assayed for three indoor allergens (dust mite, cat, and cockroach), revealed similar exposure for asthma and control groups. Sixty-nine percent of the children with asthma had IgE antibodies to dust mite, cockroach, or cat; only 27% of the control subjects were similarly sensitized (p < 0.001). Of 35 children with asthma 21 had both sensitization and significant exposure to the relevant allergen; this was true for only 3 of 22 control subjects (odds ratio, 9.5; p < 0.001). Neither sensitization nor exposure to cat allergen was common in this population. The results show that black children in inner city Atlanta are exposed to high levels of mite and cockroach allergens and that a high proportion of the children with asthma are sensitized to these allergens; the combination of sensitization and exposure is a major risk factor for asthma in this population.     

Effects of an acaricide on mite allergen levels in the homes of asthmatic children

Previous study by the current authors has shown that treating homes with D'Allergen, an acaricidal agent, can reduce bronchial hyper-reactivity in asthmatic children with house dust mite allergy. In the present study, the effects of a single D'Allergen treatment on the levels of major dust mite allergens, Der p I and Der f I was evaluated, and the duration of its effectiveness in the environment determined. Twenty randomly selected homes were treated with the acaricide and ten remained untreated. Dust samples were collected from mattresses, upholstered sofas and carpets of these homes before and 1, 2 and 4 months after treatment. The samples were then assayed for Der p I and Der f I allergens using a sandwich enzyme immunoassay. The results showed that D'Allergen was effective in reducing dust mite allergen levels in all three niches by 1.5–22.3 times below baseline values. This effect, however, was only present for 2 months, and the dust mite allergen levels increased to those of the baseline by the fourth month after treatment. These results indicated that repeated applications of the acaricide were required at 2–3 monthly intervals to obtain optimal effectiveness.     

Lung function at age 3 years: effect of pet ownership and exposure to indoor allergens

OBJECTIVE: To investigate the effect of pet ownership and exposure to indoor allergens on lung function in 3-year-old children. DESIGN: Birth cohort study. SETTING: Community. PARTICIPANTS: Children recruited prenatally and followed prospectively to age 3 years. MAIN OUTCOME MEASURES: Specific airway resistance (sRaw) (measured with body plethysmograph) at age 3 years; skin-prick tests; data on cat and dog ownership collected prospectively; allergen levels measured in dust collected from homes (high exposure defined as mite allergens >2 microg/g in mattress, and dog >10 microg/g and cat >8 microg/g allergens on the living room floor). RESULTS: There was no effect of cat or dog ownership at birth or age 3 years on lung function, and no association between lung function and mite, dog, or cat allergen exposure. Sensitized children exposed to high levels of sensitizing allergen had significantly poorer lung function (n = 49, sRaw kiloPascal per second [kPa/s]; geometric mean [GM], 1.20; 95% confidence interval [CI], 1.13-1.28) than children who were not sensitized and not exposed (n = 114; GM, 1.08; 95% CI, 1.04-1.12); not sensitized, but exposed (n = 282; GM, 1.07; 95% CI, 1.05-1.10); or sensitized and not exposed (n = 53; GM, 1.12; 95% CI, 1.06-1.18; P = .005). In a multivariate model, independent significant associates of lung function were maternal and paternal asthma, and the combination of sensitization and exposure to sensitizing allergen, with significant interaction between them. Lung function was substantially worse in sensitized and highly exposed children with both asthmatic parents (GM, 2.23; 95% CI, 1.68-2.97), compared with those with neither (GM, 1.09; 95% CI, 1.04-1.16) or just 1 of these features. CONCLUSIONS: Pet ownership, sensitization without exposure, or exposure in nonsensitized individuals have no effect on lung function. However, the combination of specific sensitization and exposure to sensitizing allergen is associated with significantly poorer lung function in early life.     

High prevalence of sensitization to aeroallergens in children 4 yrs of age or younger with symptoms of allergic disease

The assumption that sensitization to aeroallergens is rare in preschool children is based on population studies in which most subjects have little or no symptoms of atopic disease. We assessed the prevalence of atopic sensitization in children 0 to 4 yr of age presenting with symptoms of allergic disease by reviewing results of all specific immunoglobulin (IgE) tests performed in our hospital laboratory in children 4 yr of age or younger between 1985 and 2003. Tests were ordered by general practitioners or hospital‐based pediatricians in children presenting with symptoms of allergic disease. Specific IgE tests to a panel of common food and inhalant allergens were performed in 2946 children; a specific IgE concentration >0.35 kU/l was considered positive. Overall, 505 (17%) tests were positive to aeroallergens: 346 (12%) for house dust mite, 257 (9%) for dog dander, 240 (8%) for cat dander, and 197 (7%) for grass pollen. Positive tests were more common in boys (19.2%) than in girls (14.2%, p < 0.01), irrespective of age. Although sensitization to food allergens was more common in 0‐<3 yr olds, aeroallergen and food allergen showed comparable prevalence rates in 3‐<5 yr olds. Sensitization to aeroallergens is common in preschool children with symptoms of allergic disease, and more common in boys than in girls. Screening tests for allergy in infants and toddlers should include inhalant allergens.