Persistent pollen exposure during infancy is associated with increased risk of subsequent childhood asthma and hayfever.

BACKGROUND: Few studies have focused on pollen exposure and asthma in children. None have examined associations between persistent exposure to pollen in infancy and aeroallergen sensitisation and asthma in childhood. OBJECTIVES: To examine the association between higher ambient levels of pollen in the first 3-6 months of life and risk of eczema, sensitization to food and aeroallergens at 2 years and asthma or hayfever at age 6-7 years combined. METHODS: Using a birth cohort of 620 infants with a family history of allergic disease born between 1990 and 1994, we examined risk of eczema or allergic sensitization (SPT > 3 mm to at least one of cow's milk, egg white, peanut, house dust-mite, rye grass, and cat dander) by age 2 and asthma or hayfever at age 6-7. Daily ambient levels of pollen were measured during this period. RESULTS: Cumulative exposure to pollen concentrations up to 6 months was associated with aeroallergen sensitization with the highest risk occurring at 3 months (aOR = 1.34, 95% CI 1.06-1.72). Cumulative exposure to pollen up to 3 months was also associated with hayfever (aOR = 1.14, 95% CI 1.009-1.29) and between 4 and 6 months exposure with asthma only (aOR=1.35, 95% CI 1.07-1.72). CONCLUSION: Persistent pollen exposure in infancy appears to increase the risk of asthma and hayfever in children. These results support the hypothesis that there is a critical window of opportunity in early development which may be important for modification of allergic outcomes.

Pets at birth do not increase allergic disease in at-risk children.

BACKGROUND: The literature is contradictory concerning pet exposure and risk of allergic disease in childhood especially among those with a family history of allergy. OBJECTIVE: To investigate the relationship between cat and dog exposure at birth and allergic outcomes over the first 12 years in a birth cohort selected for familial allergy. METHODS: A prospective birth cohort of 620 infants with a family history of allergic diseases was recruited. Data on pet keeping, family demographics and cord blood samples were collected at birth. Information on childhood wheeze, eczema and hay fever was collected 18 times in the first 2 years, at 7 years and at 12 years. Skin prick tests were conducted at 2, 7 and 12 years, and in parents. Regression analyses were used to investigate the relevant associations while adjusting for potential confounders. RESULTS: Exposure to cats or dogs at birth showed a moderate reduction in risk of wheeze (aOR = 0.76; 95% CI 0.53, 1.09) and hay fever (aOR = 0.71; 0.49, 1.02) after 7 years of age. Protective effects were stronger in children of non-sensitized fathers (aOR wheeze 0.55; 0.31, 0.98; aOR hay fever 0.33; 0.15, 0.77 on exposure to cats alone, or cats or dogs at birth). Pet keeping was not related to cord blood IgE or sensitization from 2 to 12 years. CONCLUSIONS AND CLINICAL RELEVANCE: Pets at birth either decreased or had no effect on allergic disease up to age 12. We found no evidence that exposure to cats or dogs at birth increases the risk of allergic disease in high-risk children.

Associations between fatty acids in colostrum and breast milk and risk of allergic disease.

BACKGROUND: Exposure to n-3 polyunsaturated fatty acids (PUFA) in early life is hypothesized to offer protection against atopic disease. However, there is controversy in this area, and we have previously observed that high levels of n-3 fatty acid (FA) in colostrum are associated with increased risk of allergic sensitization. OBJECTIVE: The aim of the study was to assess the relationship between FA profile in breast milk and risk of childhood atopic disease. METHODS: A high-risk birth cohort was recruited, and a total of 224 mothers provided a sample of colostrum (n=194) and/or 3-month expressed breast milk (n=118). FA concentrations were determined by gas chromatography. Presence of eczema, asthma and rhinitis were prospectively documented up to 7 years of age. RESULTS: High levels of n-3 22:5 FA (docosapentaenoic acid, DPA) in colostrum were associated with increased risk of infantile atopic eczema [odds ratio (OR)=1.66 per 1 standard deviation increase, 95% confidence interval (CI)=1.11-2.48], while total n-3 concentration in breast milk was associated with increased risk of non-atopic eczema (OR=1.60, 95% CI=1.03-2.50). Higher levels of total n-6 FA in colostrum were associated with increased risk of childhood rhinitis (OR=1.59, 95% CI=1.12-2.25). There was no evidence of associations between FA profile and risk of asthma. CONCLUSION: In this cohort of high-risk children, a number of modest associations were observed between FA concentrations in colostrum and breast milk and allergic disease outcomes. Further research in this area with larger sample sizes is needed.

Confirmation of the association between high levels of immunoglobulin E food sensitization and eczema in infancy: an international study.

BACKGROUND: Studies of Australian infants have reported that more than 80% of those with moderate atopic eczema (AE) have high levels of IgE food sensitization (IgE-FS) that are commonly associated with IgE food allergy. OBJECTIVES: To explore the relationship between high levels of IgE-FS and AE in a large cohort of young children with eczema participating in a multi-centre, international study. METHODS: Two thousand one hundred and eighty-four subjects (mean age 17.6 months, range 11.8-25.4; 1246 males) with active eczema from atopic families from 94 centres in 12 countries were studied. Clinical history, Scoring Atopic Dermatitis index as a measure of eczema severity and CAP-FEIA measurements for total IgE and IgE antibody levels to cow milk, egg and peanut were entered into a database. If CAP-FEIA levels exceeded previously reported age-specific cut-off levels for 95% positive predictive values (PPVs) for food allergy, subjects were defined as having high-risk IgE-FS (HR-IgE-FS). RESULTS: Serum was available from 2048 patients; 55.5% were atopic. The frequency of HR-IgE-FS to milk, egg and/or peanut was the greatest in patients whose eczema developed in the first 3 months of life and the least in those whose eczema developed after 12 months (P<0.0001). In a regression analysis to allow for potential confounding factors, children with HR-IgE-FS had the most severe eczema and the youngest age of onset (P<0.001); 64% of infants with severe eczema of onset-age <3 months had HR-IgE-FS. CONCLUSION: Early-onset severe eczema in infancy was associated with HR-IgE-FS. Clinical implications Food allergies should be routinely assessed in infants with moderate or severe eczema. Capsule summary In eczematous infants, the earlier the age of onset, and the greater the severity of eczema, the greater the frequency of associated high levels of IgE-FS.

Skin prick test can identify eczematous infants at risk of asthma and allergic rhinitis.

BACKGROUND: Assessment of allergic sensitization is not routinely performed in infants and young children with eczema. OBJECTIVE: To determine whether infants who have atopic eczema (with sensitization) are at a greater risk of developing asthma and allergic rhinitis (AR) than those with non-atopic eczema (without concurrent sensitization). METHODS: The presence of eczema was prospectively documented until 2 years of age in a birth cohort of 620 infants with a family history of atopic disease. Sensitization status was determined by skin prick tests (SPTs) at 6, 12, and 24 months using six common allergens. Interviews were conducted at 6 and 7 years to determine the presence of asthma and AR. RESULTS: Within the first 2 years of life, 28.7% of the 443 children who could be classified had atopic eczema: 20.5% had non-atopic eczema, 19.0% were asymptomatic but sensitized and 31.8% were asymptomatic and not sensitized. When compared with children with non-atopic eczema in the first 2 years of life, children with atopic eczema had a substantially greater risk of asthma [odds ratio (OR)=3.52, 95% confidence interval=1.88-6.59] and AR (OR=2.91, 1.48-5.71). The increased risk of asthma was even greater if the infant had a large SPT (OR=4.61, 2.34-9.09) indicative of food allergy. There was no strong evidence that children with non-atopic eczema had an increased risk of asthma or AR compared with asymptomatic children. CONCLUSION: In children with eczema within the first 2 years of life, SPT can provide valuable information on the risk of childhood asthma and AR.

The temporal sequence of allergic sensitization and onset of infantile eczema.

BACKGROUND: Eczema is commonly associated with sensitization in infants, but the causative role of sensitization in the development of eczema has been questioned. OBJECTIVE: To determine if allergic sensitization increases the risk of developing eczema, or alternatively, if eczema increases the risk of developing allergic sensitization. METHODS: We used data from the Melbourne Atopy Cohort Study, a prospective birth cohort of 552 infants with a family history of atopic disease. The main outcomes were risk of developing eczema from 6 months to 7 years of age in asymptomatic infants; and risk of developing sensitization, as measured by skin prick tests to milk, egg white, peanut, house dust mite, rye grass pollen and cat extracts, in previously unsensitized infants. RESULTS: Sensitization to food extracts at 6 months was associated with an increased risk of developing eczema [hazard ratio (HR) 1.63, 95% confidence interval 1.13-2.35] up to 7 years of age, after excluding infants with eczema in the first 6 months. However, eczema in the first 6 months was also associated with increased risk of new sensitization at both 1 year (HR 2.34, 1.38-3.98) and 2 years (HR 3.47, 1.65-7.32). CONCLUSION: In some infants, sensitization precedes and predicts the development of eczema, while in others eczema precedes and predicts the development of sensitization. This indicates that there are multiple pathways to atopic eczema.

Food allergy and atopic dermatitis in infancy: an epidemiologic study.

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

Maternal breast milk long-chain n-3 fatty acids are associated with increased risk of atopy in breastfed infants.

BACKGROUND: Australia has one of the highest prevalence rates internationally of allergic conditions, such as asthma and eczema. Atopy is one hallmark for the development of allergic disease and predisposes to allergic inflammation in the target organs. omega-3 (n-3) fatty acids (FAs) are thought to act as precursors to the formation of less active inflammatory mediators, with the potential to reduce inflammation. OBJECTIVE: To investigate whether increased n-3 FA levels in maternal breast milk are associated with a lower risk of developing atopy in infancy. METHODS: Subjects were part of the prospective Melbourne atopy cohort study, which involved 620 children born into families where at least one first-degree relative had an atopic disease. Some 224 women (mean age 31.4+/-4.2 (SD) years, with 73.2% (n=164) having self-reported atopy) provided either a colostrum (n=194) or 3-month expressed breast milk (EBM) sample (n=118). Maternal colostrum and 3-month EBM samples were analysed for FA content by gas chromatography. Skin prick tests (SPTs) to six common allergens were performed on infants at 6, 12 and 24 months of age and on mothers who agreed at study entry. RESULTS: For infants sensitized to foods at 6 months (n=29), the total n-3 FA level in the colostrum was significantly higher (P=0.004) as were levels of individual long-chain n-3 FAs, docosoapentaenoic acid (DPA, C22:5, P=0.001) and docosahexaenoic acid (DHA, C22:6, P=0.002) than in non-sensitized infants. Infants with aero-allergen sensitization at 24 months (n=30) had higher levels of the n-3 FA, DPA (P=0.002) and DHA (P=0.007), and similarly higher total n-3 FA (P=0.009) in maternal colostrum than those infants who were not sensitized. CONCLUSION: Higher n-3 FA levels in the colostrum do not appear to confer protection against, but may be a risk factor for, the eventual development of atopy in high-risk breastfed infants.

Reducing the need for food allergen challenges in young children: a comparison of in vitro with in vivo tests.

BACKGROUND: Double-blind placebo-controlled food challenges (DBPCFC), the gold standard for the diagnosis of food hypersensitivity, are time-consuming and not without risk. We have recently reported skin prick test (SPT) weal diameters to cow's milk, egg and peanut above which infants and young children referred for investigation of suspected food allergy showed an adverse reaction on food challenge. We have termed these the "100% diagnostic SPT levels". In this study, we compare in vivo with in vitro measurement of IgE antibody levels to three common food allergens--cow's milk, egg and peanut--in infants and young children with suspected food allergy, in order to reduce the need for food challenges. METHODS: SPT and Enzyme Allergo-sorbent Test (EAST) (from 1992 to 1998) and CAP values (from 1999 to 2000) were performed in 820 children < 2 years of age with suspected allergy to cow's milk and/or egg and/or peanut. SPT levels previously shown to be diagnostic of challenge-proven allergy to cow's milk, egg and peanut were used as the "100% diagnostic SPT levels" and compared with EAST and CAP values associated with IgE food allergy according to the manufacturer's definition. RESULTS: McNemar's test showed a significant difference between the "100% diagnostic SPT levels" and positive EAST in identifying patients who did not require food challenge for cow's milk (P = 0.01), egg (P < 10-6) and peanut (P < 10-6), and a significant difference between the "100% diagnostic SPT levels" and positive CAP (P < 10-6) for egg and peanut but not cow's milk. Twenty-three per cent of food challenges which, based on the results of EAST and CAP, would have been necessary to confirm the diagnosis of food allergy were avoided by the use of the "100% diagnostic SPT levels" . CONCLUSION: The use of the "100% diagnostic SPT levels" compared with in vitro measurement of IgE antibody to cow's milk, egg and peanut reduces the need for food challenge in young children with suspected food allergy.

Specificity of allergen skin testing in predicting positive open food challenges to milk, egg and peanut in children.

BACKGROUND: The specificity of allergen skin prick testing to diagnose clinically relevant food allergy is controversial. OBJECTIVES: To determine the specificity of the allergen weal diameter to correctly identify children who react on formal open food challenges. METHODS: Over a 9-year period children referred to a tertiary allergy clinic for the evaluation of suspected food allergy were prospectively studied. Allergen skin prick testing to cow milk, egg white and peanut extracts (Dome-Hollister-Stier, Spokane, WA, USA) was undertaken using a lancet technique. All children underwent open food challenges to the relevant food(s) in a hospital clinic. Challenges were classified as positive, if objective signs were seen; negative, if the child could tolerate normal quantities of the food, daily, for one week; or inconclusive if none of the former criteria were met. RESULTS: Five hundred and fifty-five challenges were undertaken in 467 children: 339 challenges to cow milk, 121 to egg, and 95 to peanut. Fifty-five percentage of challenges were positive, 37% negative, and 8% inconclusive. For each food it was possible to identify a skin weal diameter at, and above, which negative reactions did not occur: cow milk, 8 mm; egg, 7 mm; peanut, 8 mm. In contrast, positive reactions could occur with a skin wheal diameter of 0 mm. CONCLUSIONS: In this high risk referral population it was possible to define skin weal diameters to egg, milk and peanut above which open oral food challenges were positive (100% specificity). By utilizing these measurements the need for formal food challenges can be reduced.

The association of atopic dermatitis in infancy with immunoglobulin E food sensitization.

OBJECTIVE: To prospectively investigate the association of high levels of immunoglobulin E (IgE) sensitization to foods and the presence of atopic dermatitis (judged by reported topical steroid use during the first 16 months of life) in a birth cohort of 620 Australian children "at risk" of allergic disease because of family history. RESULTS: A total of 559 of the children in the cohort were fully evaluated, and the cumulative prevalence of atopic dermatitis was 24%. More children in the cohort who had atopic dermatitis had strongly positive skin test results (> or = 4+, histamine equivalent units, > or = approximately 6-mm wheal), consistent with IgE food sensitization to either cow's milk, egg, or peanut at 6 months (22% vs 5%, chi(2) = 35; P < 10(-6)) and at 12 months (36% vs 11%, chi(2) = 41; P < 10(-6)) than those without atopic dermatitis. The calculated attributable risk percent for IgE food sensitization as a cause of atopic dermatitis was 65% and 64% at these times. In a separate group of infants with severe atopic dermatitis, the equivalent rates of IgE food sensitization at 6 months was 83% and at 12 months, 65%. CONCLUSION: IgE food sensitization is a major risk factor for the presence of atopic dermatitis in infancy.

Role of food protein intolerance in infants with persistent distress attributed to reflux esophagitis.

BACKGROUND: Distressed behavior is common in infants and is often attributed to gastroesophageal reflux (GER) or food protein intolerance. OBJECTIVE: To examine the effect of a hypoallergenic amino acid-based infant formula (AAF) on distressed behavior and GER symptoms in infants who failed to respond to extensively hydrolyzed formula and antireflux medications. STUDY DESIGN: Nineteen distressed infants (9 boys and 10 girls; median age, 5.0 months) with presumed GER underwent gastroscopy (n = 17) and esophageal 24-hour pH monitoring (n = 14). Double-blind placebo-controlled (DBPC) formula challenges of AAF versus previously besttolerated formula were conducted. RESULTS: Nine infants had histologic evidence of esophagitis, and 9 had inflammatory changes in the stomach and/or duodenum. Symptoms remitted in all infants within 2 weeks of the start of feeding with AAF. On DBPC challenge after a median period of 3 months of receiving AAF, 12 infants were intolerant to active formula (distress score, 287 vs 580 min/wk,P =. 01; symptom score, 23.1 vs 36.1, P =.03). Seven infants did not relapse and were considered tolerant (distress score, 470 vs 581, P =.77; symptom score, 29.5 vs 20.2; P =.89). CONCLUSION: Treatment with AAF may reduce distressed behavior and symptoms of GER in infants with food protein intolerance.

Infantile colic and food hypersensitivity.

In this article, some aspects of the phenomenon of infantile colic or fussing and crying behavior in early infancy are reviewed. The major points addressed are as follows: 1) evidence that infants with colic differ significantly in their pattern of distressed behavior from noncolicky infants; 2) the evidence of colic in children with known food allergy; 3) the incidence of food allergy in children with colic; 4) the outcome of trials focusing on the dietary management of colic; 5) the outcome of studies involving behavior modification in colic; 6) the outcome of a preliminary trial of modification of maternal diet in very young infants with colic; and 7) findings of a systematic review of different treatments for colic.

Clinical spectrum of food allergy in children in Australia and South-East Asia: identification and targets for treatment.

The prevalence of atopic diseases is increasing worldwide for reasons that are not clear. Food allergies are the earliest manifestations of atopy. This review defines the foods most commonly involved in allergic reactions and identifies an emerging group of syndromes in which food allergy is involved. A study of the frequency of food allergies in Australia and South-East Asia has recently shown that egg, cow's milk and peanut are the most common food allergens in Australia, but there were divergent results from different regions of South-East Asia. It is not clear whether the differences in reactivity to foods are due to genetic or cultural factors, but the findings raise the possibility that genetic susceptibility to food allergy may operate at the T-cell level modulated by the major histocompatibility complex. The Melbourne Milk Allergy Study defined a wide range of clinical symptoms and syndromes that could be reproduced by dietary challenge. A subsequent analysis of the infants with hypersensitivity to cow's milk and other multiple food proteins identified a new syndrome, multiple food protein intolerance of infancy. Food challenges demonstrated reactions developing slowly days after commencement of low-allergen soy formula or extensively hydrolysed formula. Follow-up at the age of 3 years showed that most children with this disorder tolerated most foods apart from cow's milk, egg and peanut. Atopic dermatitis affects about 18% of infants in the first 2 years of life. In a community-based study we have shown a very strong association (RR 3.5) between atopic dermatitis and infants with immunoglobulin E allergy to cow's milk, egg or peanut. Family studies on these infants have shown a link between atopic dermatitis and the genomic region 5q31 adjacent to the interleukin-4 gene cluster. Infantile colic (distress) affects 15-40% of infants in the first 4 months of life. Many theories of causation have been proposed, but a study from our centre showed that dietary modification, particularly that of breastfeeding mothers whose infants present with colic before the age of 6 weeks, alleviated symptoms. Colic associated with vomiting has been attributed to gastro-oesophageal reflux (GOR). This has been considered primarily a motility disorder, but a secondary form resulting from food protein intolerance has been described recently. We have also recently identified a group of infants with distressed behaviour attributed to GOR who have failed to respond to H2-receptor antagonists, prokinetic agents and multiple formula changes. Symptoms resolved on commencement of an elemental amino acid-based formula. In two-thirds of the patients, symptoms relapsed when challenged with low-allergen soy formula or extensively hydrolysed formula. We propose that a period of food protein intolerance is a part of the normal development of the immune system as it encounters common dietary proteins in infancy and early childhood. Future targets for research are development of appropriate dietary and management strategies for these entities and identification of genetic markers for these disorders.

Graded compression ultrasonography in the assessment of the "tough decision" acute abdomen in childhood.

The diagnosis of acute appendicitis in childhood is frequently difficult. In some situations the need to operate is clear, but in others the decisions may be much "tougher" because the clinical findings are equivocal. This is a retrospective study of a consecutive series of 253 children presenting with "acute abdominal pain? appendicitis" who had graded compression ultrasonography (GCUS) because the clinical scenario did not warrant immediate laparotomy. This represents 30% of all cases seen in the study period. The aim of the study was to examine the role of GCUS and a clinical scoring system (the Alvarado score) in patients in whom the diagnosis is uncertain.

The Melbourne House Dust Mite Study: long-term efficacy of house dust mite reduction strategies.

BACKGROUND: Asthma severity among mite-sensitized individuals appears to be related to the degree of mite allergen exposure. OBJECTIVES: The objective of this study was to assess the long-term effectiveness of mite avoidance measures in the homes of asthmatic children in Melbourne, Australia. METHODS: The concentration of house dust mite allergen (Der p 1) was measured on the child's mattress surfaces and bedroom floors in 85 homes on 10 occasions over a 16-month period. After the first three visits, all mattresses were covered with a semipermeable encasement, and carpeted bedroom floors were randomly allocated to regular applications of a placebo or an "anti-mite" shampoo. RESULTS: The concentration of Der p 1 recovered was initially high in the carpeted bedrooms (n = 66) (41.1, 95% confidence interval, 30.7 to 55.0 microg Der p 1 per gm) and mattresses (n = 85) (39.6, 27.2 to 57.7). During the initial observation period the concentration of mite allergen fell in the treatment, placebo, and parental control groups. During the seven treatment periods, no differences were seen between the Der p 1 concentrations in the groups using the "anti-mite" shampoo, placebo shampoo, or the parental control group (e.g., at visit 4; 12.6, 8.2 to 19.5; 14.8, 8.6 to 25.1; and 12.0, 8.1 to 17.7 microg/gm, respectively). In contrast, the concentration of Der p 1 in samples from uncarpeted floors and mattress encasements was low (4.1, 2.1 to 8.0 microg/gm and 4.2, 2.6 to 6.5 microg/gm, respectively) and insufficient dust for analysis was frequently obtained from these sites. CONCLUSIONS: There was no additional benefit from the use of an "anti-mite" shampoo. The absence of carpets and the use of mattress encasements was a useful long-term strategy for mite allergen avoidance.

The Melbourne house dust mite study: eliminating house dust mites in the domestic environment.

BACKGROUND: Hypersensitivity to house dust mite allergens is associated with increased asthma morbidity. Asthma severity appears to be related to the degree of mite allergen exposure. Short-term studies suggest that complete avoidance reduces disease severity. OBJECTIVE: The study was designed to assess the effect of different mattress covers and floor coverings on mite allergen concentrations in the homes of mite-sensitive children with asthma in the city of Melbourne, Australia. METHODS: Mite allergen Der p 1 concentration was measured on mattress covers, mattress surfaces, and carpeted and uncarpeted floors in 107 dwellings; and measurement was performed on three occasions over a 5-month period. After the first sampling, all mattress covers and impermeable encasements were permanently removed. RESULTS: The initial geometric mean concentrations of Der p 1 (micrograms per gram of fine dust) from the surfaces of sheepskin, wool, and cotton mattress coverings were greater than those from the surfaces of impermeable mattress encasements (116, 113, and 19 vs 0.4) (p < 0.001); corresponding concentrations on the underlying mattresses were 142, 38, 20, and 0.6, respectively (p < 0.05 to 0.001). At the end of the study these mattress surface concentrations were 79, 65, 9.7, and 3.1, respectively. In 24 dwellings an uncarpeted room was adjacent to a carpeted room. At each visit the concentration of Der p 1 in uncarpeted rooms was below the reported threshold for sensitization and significantly less than that in the adjacent carpeted room. CONCLUSION: In homes of children with asthma, "asthmogenic" concentrations of Der p 1 were found on nonencased mattresses and carpeted floors, but the use of impermeable mattress encasements and carpet exclusion were associated with concentrations of Der p 1 below the reported threshold for sensitization.