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.     

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.     

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.     

House dust mite exposure in asthmatic and healthy children: the difference is carpeting

Aim - To determine whether house dust mite (HDM) exposure in living rooms and bedrooms is higher in asthmatic children than in those of age and sex matched healthy children, living in the same area. Methods - Types of floor-coverings were recorded and dust samples were collected by vacuum cleaning the total area of living rooms and bedrooms; Der p I and Der p II per gram fine dust concentrations were assessed. Twenty-five asthmatic children (RAST HDM >= class 3, age 6–12 years) and 25 healthy children participated in the study. Results - The frequency of cleaning and prevalence of smooth floor-coverings in bedrooms of asthmatic children were significantly higher. There were no differences in living rooms in this respect. The amount of fine dust/m² floor space was significantly lower in bedrooms of asthmatic children. Concentrations of HDM were low and no differences in Der p I and Der p II concentrations were observed between the two groups (asthmatic children: Der p I living room: 1.1 (0.04 - 59.4 μg/ g), bedroom: 0.5 (below detection - 19.3 μg/g); nonasthmatic children: Der p I living room: 1.4 (below detection - 27.5 μg/g), bedroom: 0.9 (below detection - 68.8 ug/g. Smooth floor coverings contained significantly less fine dust, Der p I, and Der p II than carpeted floors. Conclusions - Low HDM concentrations are a general finding in Dutch dwellings in the present generation of children. We observed a higher cleaning frequency, and more smooth floor coverings in bedrooms of asthmatic children than of healthy children, yet HDM concentrations were not significantly different. The latter can be explained by the observation that only 40% of the asthmatic children had smooth floor coverings in their bedrooms. Smooth floor coverings contain less fine dust and lower concentrations of Der p I and Der p II than carpeted floors.     

The influence of exposure to house dust mite, cat, pollen and fungal allergens in the home on primary sensitisation in asthma

The homes of 68 atopic asthmatic children were studied to estimate the concentrations of perennial and seasonal aeroallergens (Der pl, Fel d1, grass pollen, tree pollen, Cladosporium , Aspergillaceae and Alternaria ) to which children were likely to have been exposed during their first few months of life, by sampling in the child's month of birth. There was a strong association between the presence or absence of the house dust mite allergen Der p1 in the air with the skin test and IgE antibody test results (p < 0.001), with a similar association for cat allergen Pel d 1 (p < 0.01), when using a low volume sampler (equivalent to the minute tidal volume of a small baby). No significant correlation was found between levels of allergen in carpet dust and air in the same room. There was a strong indication that the presence of a cat at birth was linked with a higher risk of development of allergy to cat, but high levels of Fel d 1 were sometimes found in homes even when there was no cat present, indicating that allergen may be introduced from other sources. The levels of tree pollen were significantly higher in the homes of tree pollen-allergic children than in the homes of patients without this sensitivity (p < 0.01); and the degree of sensitivity, determined by RAST, correlated significantly to the level of tree pollen in the home (p < 0.001). However, no relationship was found between specific sensitivity and the levels of Cladosporium , Aspergillaceae, Alternaria or grass pollen measured in the homes. The effect of high allergen exposure was most prominent in children under 7 yr and not beyond that age.     

Vacuum cleaning decreases the levels of mite allergens in house dust

To investigate the capacity of chemical treatment of surfaces and the difference in capacity among common vacuum cleaners to reduce mite allergen content in house dust, we recruited 52 families with allergic children. Ten families used their central vacuum cleaners. Forty-two families were randomly divided into four groups with 10 or 11 families in each. These families used cither new vacuum cleaners with either HEPA (High Efficiency Paniculate Air) or micro-filters, or their own vacuum cleaners with either tannic acid or placebo. Dust samples were collected from carpets and upholstered furniture in the living rooms and from the mattresses of the children at Days 0, 7, 21, and 35. Der p I and Der f I allergens were determined by sandwich ELJSA, After one week, tannic acid reduced the concentration of mite allergens/g of dust and the total amount/sampling area by 30% and 34%, respectively (p < 0.05), but there was no significant decrease in relation to placebo. After 5 weeks, central, HEPA- and micro-filter vacuum cleaners decreased the mite allergen concentration by 10–50% (p < 0.05) and the total amount of mite allergen from the investigated areas by 50–85% (p < 0.01). In relation to the placebo group the decrease was significant for HEPA-and micro-filter vacuums (p < 0.05), The total amount of mite allergens/ sampling area was more significantly (p < 0.05) reduced than the con-centration/g of dust. We conclude, that tannic acid reduces mite allergen concentrations in dust and total amount/sampling area for a short period of time. Central, HEPA- or micro-filter vacuum cleaners reduce mite ellergen concentrations and still more the total amount of mite allergen in house dust when used regularly for long periods. Therefore, when the total house is thoroughly cleaned, tannic acid should be applied to car pets and upholstery and low mite allergen levels maintained by using modern vacuum cleaners.     

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.     

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.     

Allergens in urban schools and homes of children with asthma

To cite this article: Permaul P, Hoffman E, Fu C, Sheehan W, Baxi S, Gaffin J, Lane J, Bailey A, King E, Chapman M, Gold D, Phipatanakul W. Allergens in urban schools and homes of children with asthma. Pediatr Allergy Immunol 2012: 23: 543-549. ABSTRACT: Background: Most studies of indoor allergens have focused on the home environment. However, schools may be an important site of allergen exposure for children with asthma. We compared school allergen exposure to home exposure in a cohort of children with asthma. Correlations between settled dust and airborne allergen levels in classrooms were examined. Methods: Settled dust and airborne samples from 12 inner-city schools were analyzed for indoor allergens using multiplex array technology (MARIA). School samples were linked to students with asthma enrolled in the School Inner-City Asthma Study (SICAS). Settled dust samples from students' bedrooms were analyzed similarly. Results: From schools, 229 settled dust and 197 airborne samples were obtained. From homes, 118 settled dust samples were obtained. Linear mixed regression models of log-transformed variables showed significantly higher settled dust levels of mouse, cat and dog allergens in schools than homes (545% higher for Mus m 1, estimated absolute difference 0.55?μg/g, p?相似文献   

Effect of montelukast on exhaled NO in asthmatic children exposed to relevant allergens

The level of exhaled nitric oxide (FENO) is increased in house dust mite (HDM)-sensitized asthmatic children after exposure to HDM antigen, and inhaled steroids can prevent this increase. The aim of this study was to evaluate whether montelukast could prevent an increase in FENO levels in allergic asthmatic children after a brief period of exposure to relevant allergens. Sixteen children were evaluated at the residential house 'Istituto Pio XII' (Misurina, Bellunio, Italy) in the Italian Alps, a dust mite-free environment. FENO levels were evaluated before ( t ₀) and immediately after ( t ₁) the children were exposed to HDM allergens for 2 weeks in their homes at sea level. No significant difference in FENO was observed in the fluticasone-treated group of children after 2 weeks at sea level. In the group treated with montelukast, an increase in FENO was observed between t ₀ and t ₁, which failed to reach statistical significance. These preliminary data suggest that oral montelukast could be effective in preventing the relapse in airway inflammation in allergic asthmatic children who are occasionally exposed to relevant allergens for a short period of time.     

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.     

Variation of dust endotoxin concentrations by location and time within homes of young children

Ownby DR, Peterson EL, Williams LK, Zoratti EM, Wegienka GR, Woodcroft KJ, Joseph CLM, Johnson CC. Variation of dust endotoxin concentrations by location and time within homes of young children.
Pediatr Allergy Immunol 2010: 21: 533–540.
© 2010 John Wiley & Sons A/S Endotoxin may affect the development of allergic disease in childhood but little is known about endotoxin variation within homes. We sought to determine endotoxin concentration agreement within homes when five locations were each sampled twice 5 months apart. Endotoxin was measured using the recombinant Limulus factor C assay in dust samples from 585 homes of children enrolled in a prospective study and again in 335 homes 5 months later. The five locations sampled in each home were the child’s bedroom floor, child’s bed, mother’s bedroom floor, mother’s bed and living room floor. Concentrations of 4 allergens (Can f 1, Fel d 1, Der f 1 and Bla g 2) were also measured from the child’s bedroom floor. In pair‐wise comparisons, endotoxin concentrations in all locations within each home were significantly different from all other locations (p < 0.001) except for the child’s and mother’s bedroom floors (p = 0.272). Spearman correlations between endotoxin concentrations from the different locations were all statistically significant (p < 0.05) but of modest magnitude (r = 0.24–0.54). Similarly, correlations at each site over the 5 month observation interval were statistically significant but modest (r = 0.17–0.44). Pets and season of the year did not affect correlations, although correlations were lower if the floor was not carpeted. Endotoxin concentrations at all locations were minimally correlated with allergen concentrations in both negative and positive directions (r = ?0.12 to 0.12). We conclude that a single measurement of endotoxin from a home dust sample provides an imprecise estimate of dust endotoxin concentrations in other locations within the home and over a relatively short observation interval.     

Effects of an acaricide on asthmatic children with house dust mite allergy

D'Allergen is a recently available acaricidal and allergen reducing agent. To study any beneficial effects of treating houses with this agent in asthmatic children with dust mite allergy, histamine bronchial responsiveness was measured in 18 children before and 6–8 weeks after their homes were treated with the agent. Comparisons were with nine similar asthmatics whose homes were not treated. The mean provocative concentration of histamine causing a 20% fall in forced expiratory volume in 1s (PC₂₀) increased from 1.02mg/L to 2.07mg/L in all 18 children who were studied (1.01 doubling doses). Bronchial responsiveness was relatively unchanged in a well matched control group of nine children studied over comparable time periods (PC₂₀ pre was 1.25 mg/L, PC₂₀ post was 0.67 mg/L). The results suggest that treating homes with D'Allergen reduces bronchial reactivity in asthmatic residents with house dust mite allergy.     

CC chemokine receptor expression in childhood asthma is influenced by natural allergen exposure

Chemokines and their receptors may play an important role for leukocyte trafficking in allergic inflammation. Aim was to evaluate whether expression of chemokine receptors CCR4 and CCR8 on cells obtained by sputum induction from asthmatic allergic children may be influenced by house dust mite (HDM) allergen natural exposure. Twenty-one children (7-13 yr) with moderate asthma and sensitized to HDM were evaluated during a prolonged period of allergen avoidance (T0) and after a period of natural allergen exposure (T1). At each time point of sputum induction, lung function evaluation, exhaled nitric oxide (eNO) measurements were performed. At T1, CCR4 and CCR8 expression on sputum-induced cells increased from 28.4% +/- 2.9% and 25.8% +/- 1.9%, to 41.1% +/- 4.2% and 37.5% +/- 2.0%, respectively (p < 0.05 and p = 0.01). After allergen exposure, both sputum eosinophils (from 5.2% +/- 2.0% to 12.1% +/- 4.1%, p < 0.01) and eNO (from 15.1 +/- 2.2 ppb to 24.2 +/- 5.8 ppb, p < 0.05) showed significant increase. Lung function tests presented significant deterioration of Forced Expiratory Flow at 25-75% of Vital Capacity (FEF(25--75)) (p < 0.05) and increase of residual volume (p = 0.002). Significant changes in CC chemokine receptor expression in sputum-induced cells in asthmatic children in response to HDM exposure have been observed leading to consider the relevance of CCR4 and CCR8 in allergic asthmatic inflammation.     

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.     

屋尘螨皮下特异性免疫治疗的哮喘患儿肺功能及免疫学动态变化

目的：动态观察屋尘螨变应原皮下特异性免疫治疗对哮喘患儿的肺功能和免疫学影响。方法：屋尘螨过敏的轻中度哮喘患儿32例,分成治疗组(n=15)和对照组(n=17)。治疗组吸入糖皮质激素的同时加用屋尘螨变应原皮下特异性免疫治疗,对照组仅予吸入糖皮质激素治疗。检测治疗前、治疗后3月、6月、12月、18月、24月肺通气功能,观察治疗前、治疗后12月及24月哮喘发作次数并测定血清总IgE、屋尘螨特异性IgE、屋尘螨特异性IgG4、嗜酸细胞阳离子蛋白（ECP）、IL-10、IL-4及IFN-γ的变化。结果：治疗组患儿治疗后肺通气功能各项参数稳定在正常或接近正常水平;无哮喘急性发作病例的百分率治疗后高于治疗前,随治疗时间的延长而增加（P<0.05）;治疗后屋尘螨特异性IgG4高于治疗前,随着治疗时间延长而增加（P<0.01）;治疗后血清总IgE、屋尘螨特异性IgE、ECP、IL-10、IL-4、IFN-γ水平与治疗前比较,差异无统计学意义。对照组患儿治疗前后各项指标比较,差异均无统计学意义。结论：屋尘螨过敏的轻中度哮喘患儿经屋尘螨变应原皮下特异性免疫治疗2年后,肺通气功能保持正常或接近正常,无哮喘急性发作病例增加,可能与血清屋尘螨特异性IgG4浓度增高有关。［中国当代儿科杂志,2010,12（9）：715-719］     

House dust mite sensitivity in childhood asthma.

The clinical features of perennial asthmatic children with a skin or bronchial reaction to the house dust mite (Dermatophagoides pteronyssinus) were compared with those of asthmatic children without mite sensitivity. Mite sensitive asthma was characterised by an early age of onset of symptoms, these being predominantly nocturnal. A history of wheezing precipitated by dust exposure, during vacuuming, bedmaking, or dusting was present in 52% of cases. Asthmatic children with mite sensitivity were more likely to have been born at the time of the year when mite counts were highest. This was consistent with the idea that allergy may be associated with a period of susceptibility to sensitisation in early infancy.     

House dust mite allergen reduction and allergy at 4 yr: Follow up of the PIAMA-study

Exposure to high allergen levels in early life is a risk factor for the development of allergy. We previously reported limited effects of mite allergen impermeable mattress covers in the prevention and incidence of asthma and mite allergy (PIAMA) cohort at the age of 1 and 2 yr. We now present the results of follow-up at 4 yr objectives. To examine the effects of early reduction of house dust mite (HDM) allergen exposure by means of mattress covers on the incidence of allergy and asthma symptoms in the PIAMA birth cohort at the age of 4 yr. High-risk children (allergic mother) were prenatally recruited and randomly allocated to three groups; receiving mite allergen impermeable mattress covers (n = 416), placebo covers (n = 394) or no intervention (n = 472). At 4 yr of age, atopy was assessed by questionnaire; specific Immunoglobulin E (IgE) to inhalant and food allergens was measured in serum. Dust samples collected from the children's mattresses were analysed for mite allergens. Dermatophagoides farinae1 allergen (Der f 1) levels in dust were reduced in the active group. However, Dermatophagoides pteronissinus 1 (Der p 1) levels, sensitization and atopic symptoms were similar in all groups. We found no effect of mite allergen impermeable mattress covers on sensitization and atopy at 4 yr. Moreover, the allergen reducing effects of the covers had disappeared for one of the two mite allergens that were measured.     

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.     

Low frequency of positive skin tests in asthmatic patients infected with Schistosoma mansoni exposed to high levels of mite allergens

Helminthic infections and allergic diseases are highly prevalent in many parts of the world. Although skin reactivity to indoor allergens is decreased in subjects from helminthic endemic areas, the degree of exposure to mite allergens has not yet been investigated in these areas. This study evaluated the association between exposure to dust mites and skin reactivity to mite allergens in subjects with a history of wheezing in the last 12 months selected from a rural endemic area for schistosomiasis (group I, n = 21), and two non- Schistosoma mansoni endemic locale, a rural area (group II, n = 21) and a urban slum area (group III, n = 21). All subjects were evaluated by skin prick tests with mite allergens, and for total and specific immunoglobulin E (IgE) against dust mites, antibodies for S. mansoni , and for intestinal parasites. Dust samples from each subjects' home were quantified for mite allergen and species of the mite identification. Except for S. mansoni infection which was more prevalent in group I than in groups II and III (p < 0.0001), the prevalence of intestinal parasites, and total and specific IgE levels were similar for all groups. Despite the levels of mite allergens and specifically to Der p 1 detected in dust samples of subjects home from all three areas, the frequency of positive skin reactivity to mite antigens was significantly lower (19.0%) in subjects from group I relative to group II (76.2%) and group III (57.1%; p < 0.001). This result suggests that S. mansoni infection could modulate the immediate hypersensitivity skin response to mite allergens in highly exposed subjects.