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.     

Concentrations of cat (Fel d 1), dog (Can f 1) and mite (Der f 1 and Der p 1) allergens in the clothing and school environment of Swedish schoolchildren with and without pets at home

To investigate whether our hypothesis that cat and dog owners bring allergens to public areas in their clothes was true or not, we studied the levels of Fel d 1, Can f 1, Der p 1 and Der f 1 in dust from the clothes and classrooms of children in a Swedish school. We also investigated the levels of allergen in different areas in the four classrooms used by the children. Thirty-one children were selected in four classes, forming three groups: cat owners, dog owners and children without a cat or dog at home. Furthermore, a group of children with asthma was included. Cat and dog allergens were detected in all 57 samples from clothes and classrooms. Mite allergen Der f 1 was detected in low concentrations in 6 out of 48 and Der p 1 in 5 out of 46 samples investigated. The concentrations of Can f 1 were higher than those of Fel d 1 in samples from clothes (geometric mean: 2676 ng/g fine dust and 444 ng/g) and classrooms (Can f 1: 1092 ng/g, Fel d 1: 240 ng/g). The dog owners had significantly higher concentrations of Can f 1 (8434 ng/g fine dust) in their clothes than cat owners (1629 ng/g, p <0.01), children without cat or dog (2742 ng/g, p < 0.05) and children with asthma (1518 ng/g, p < 0.001). The cat owners did not have significantly higher levels of Fel d 1 (1105 ng/g) in their clothes compared to the other three groups (D: 247 ng/g, nCnD: 418 ng/g, A: 386 ng/g) but the levels were significantly higher than for all children without a cat at home (345 ng/g, p < 0.05). No concentrations of mite allergen and low concentrations of Fel d 1 and Can f 1 were found in the children's hair. There were significantly higher concentrations of Fel d 1 and Can f 1 in dust from curtains than in samples from floors and bookshelves (p < 0.05). There was no significant difference between the allergen concentrations in samples from curtains and from desks and chairs, including the teachers' chairs, the only upholstered furniture in the rooms. Our results support the hypothesis that cat and dog owners bring allergens to public areas in their clothes and support other studies showing that textiles and upholstered furniture function as reservoirs of cat and dog allergens. Thus, children with asthma and other allergic diseases will be exposed to cat and dog allergens at school and by contact with pet owners, even if they avoid animal allergens at home.     

Analysis of basophil activation by flow cytometry in pediatric house dust mite allergy

Detection of allergen‐induced basophil activation by flow cytometry has been shown to be a useful tool for allergy diagnosis. The aim of this study was to assess the potential of this technique for the diagnosis of pediatric house dust mite allergy. Quantification of total and specific IgE and basophil activation test were performed to evaluate mite allergic (n = 24), atopic (n = 23), and non‐allergic children (n = 9). Allergen‐induced basophil activation was detected as a CD63‐upregulation. Receiver operating characteristics (ROC) curve analysis was performed to calculate the optimal cut‐off value of activated basophils discriminating mite allergic and non‐allergic children. ROC curve analysis yielded a threshold value of 18% activated basophils when mite‐sensitized and atopic children were studied [area under the curve (AUC) = 0.99, 95% confidence interval (CI) = 0.97–1.01, p < 0.001] with a sensitivity and specificity of 96% for 16 μg/ml mite extract. Analysis of the data obtained with 1.6 μg/ml mite extract defined a cut‐off value of 8% activated basophils (AUC = 0.96, 95% CI = 0.91–1.01; p < 0.001) with a sensitivity of 82% and specificity of 100%. Comparison between mite allergic and non‐allergic children produced a cut‐off of 8% activated basophils (AUC = 1.0) with 16 μg/ml allergen extract and a sensitivity and specificity of 100%. The same threshold and specificity values were obtained with 1.6 μg/ml extract (AUC = 97%, 95% CI = 0.92–1.02; p < 0.001) but sensitivity decreased to 83%. Two atopic children showed negative skin prick and basophil activation tests and high specific IgE (>43 kU/l) values for Dermatophagoides pteronyssinus allergen. They also showed positive prick (wheal diameter >1.0 cm) and basophil activation (>87%) tests and high specific IgE (>100 kU/l) with shrimp allergen. Shrimp sensitization was demonstrated by high levels of Pen a 1‐specific IgE (>100 kU/l). Cross‐reactivity between mite and shrimp was confirmed by fluorescence enzyme immunoassay (FEIA‐CAP) inhibition study in these two cases. This study demonstrated that the analysis of allergen‐induced CD63 upregulation by flow cytometry is a reliable tool for diagnosis of mite allergy in pediatric patients, with sensitivity similar to routine diagnostic tests and a higher specificity. Furthermore, this method can provide additional information in case of disagreement between in vivo and in vitro test results.     

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.     

House dust mite allergen levels in carpeted sleeping accommodation are higher in private houses than public places

OBJECTIVE: To compare mite allergen levels in carpeted sleeping accommodation in private dwellings and public places. METHODS: The concentration of Dermatophagoides pteronyssinus Group 1 allergen in house dust was measured in mat-tresses and bedroom floors in 12 homes, 5 hotels, 11 child care centres and a university hall of residence. Indoor temperature and relative humidity were also measured. A questionnaire clarified details regarding the age of the building, age of the carpet, method and frequency of cleaning, frequency of room use and use of air-conditioning. RESULTS: Median allergen levels in mattresses and carpets in private homes (21.1 and 20.6 micro g/g dust, respectively) were significantly higher than in public places (2.5 and 3.1 micro g/g, respectively; P < 0.0001). Mean relative humidity was significantly higher in private houses (68.5%; 95% CI 67.2-69.3%) than in public places (56.4%; 95% CI 52.7-60.1%; P < 0.0001). CONCLUSIONS: Carpeted sleeping accommodation in public places has lower house dust mite allergen levels than private houses. Lower levels of relative humidity may be an important component of the explanation.     

The combined influence of immunotherapy and mite allergen reduction on bronchial hyperresponsiveness in mite-sensitive asthmatic children

Encasings for mattresses, blankets and pillows in combination with mite allergen reduction on the floor have proved effective in reducing bronchial hyperreactivity of mite-allergic children. We studied the effect of combining the use of encasings with specific immunotherapy in comparison to the use of encasings alone (control group). Twenty mite-allergic children (Skin Prick Test, RAST, mean age 10 years) with asthma and high domestic mite allergen exposure (>2 μg Der p 1+ f 1/g mattress dust) were included in our study. The concentration of these major allergens as well as specific and nonspecific bronchial hyperreactivity (PC₂₀ FEV₁ histamine) were assessed before, 6 months after and 1 year after start of treatment. All children received elongated polytetrafluorethylene (ePTFE; Goretex/Intervent Allergy Bedding System) – encasings. A subgroup of eight children were treated additionally by specific immunotherapy with a partially purified mite extract (ALK Scherax) and a maximum dose of 100 000 SQ-U Der p + f. Initially both groups were comparable with respect to the parameters assessed. In 80% of children, encasings reduced Der p 1 and Der f 1 concentrations on the mattress to below 3% of the initial values (P < 0.01). The median reduction was 99%. PC₂₀ FEV₁ histamine increased from 0.4 to 1.4 mg/dl (median) in the combined group with immunotherapy and encasings (P < 0.05) and remained essentially unchanged in the control group. PC₂₀ FEV₁ Der p did not increase significantly in either group. Conclusion Specific immunotherapy with allergen extracts is an effective adjunct to encasings. Encasings, a key factor for reducing Der p 1 and Der f 1 on the mattress, should be used in combination with other avoidance measures (e.g. removal of carpets) in order to improve allergen-induced bronchial hyperreactivity. Received: 20 January 1997 / Accepted in revised form: 31 July 1997     

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.     

Dust mite allergens are carried on not only large particles

The major obstacle for the successful measurement of airborne mite allergen is its very low concentration in the absence of vigorous disturbance. The aim of this study was to investigate the particle size distribution of group 2 dust mite allergen using an amplified ELISA system. Air sampling was performed using an Andersen sampler placed in the centre of the room, 1.2 m above floor level (airflow rate28.7 l/min). This is a multistage, multiorifice cascade impactor that is comprised of six stages. Any particle greater that 4.7 μm should impact on stages 1 and 2, whilst stages 3–6 measure the predominantly respiratory range. The sampling was carried out for 30 min after 15 min of vigorous disturbance (vacuum cleaning without bag and filter). Der p 2 was measured using mAb‐based ELISA with the AmpliQ amplification kit (Dako Ltd, Cambridgeshire, UK). The sensitivity was increased ˜15‐fold as compared with standard assay, bringing the level of detection to 300 pg/ml. The majority of airborne Der p 2 (79.4%) was carried on large particles (> 4.7 µm). However, a small but important proportion of airborne Der p 2 (20.6%) was associated with small particles(1.1–4.7 µm). It is worth noting that all the levels measured were below the detection limit of standard assay. In conclusion, we have shown that using an amplification system, airborne mite allergen previously undetectable owing to its low concentration can be quantified. Group 2 dust mite allergen is carried not only on large particles. A small, but potentially significant proportion of this airborne allergen is associated with small particles which, when inhaled, may penetrate deep into the human respiratory tract.     

Double-blind placebo-controlled study of sublingual immunotherapy with house dust mite extract (D. pt.) in children

Safety and efficacy of sublingual (sublingual-swallow) immunotherapy (IT) with house dust mite extract were evaluated in 30 children (6 - 15_2/3 years of age) over the first 12 months of an ongoing study. The cumulative dose was 570 μg Der p I (five times that administered with subcutaneous therapy). Safety: One patient on active treatment dropped out after 8 weeks because of a subjective feeling of severe weakness, questionably induced by the therapy. Five patients on active therapy and one patient on placebo reported minor local side effects. Efficacy: Pulmonary symptoms were reduced after 12 months in actively treated asthmatics, but this was not consistent with the lack of improvement in bronchial reactivity, skin sensitivity and specific IgG and IgG4 against D. pt. in this group. In patients with rhinitis nasal sensitivity was reduced in the placebo group without concomitant improvement in the nasal symptom score. Specific IgE (D. pt. and D. f.) in creased significantly more in the active treatment group after 3 and 12 months. We conclude that sublingual IT over 12 months with the fivefold Der p 1 dose of subcutaneous IT was well tolerated, but there was no consistent clinical or immunological benefit compared to placebo.     

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.     

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.     

The determinants of dust mite allergen and its relationship to the prevalence of symptoms of asthma in the Asia-Pacific region

The role that house dust mites play in the primary causation of asthma is controversial. Approximately thirty-six 10-yr-old children in each of 10 centres in the Asia-Pacific region participated. Researchers collected dust from mattresses and living room floors using standardized procedures. Der p1 and Der f1 were analysed using a double monoclonal antibody enzyme-linked immunosorbent assay. Geometric mean allergen levels were calculated for each centre. An ecological analysis was conducted to show the regression of the geometric mean allergen level, using the highest household level, against asthma symptom and severity prevalence data from the International Study of Asthma and Allergies in Childhood, Phase I. Among children aged 13–14 yr, the change in asthma symptom prevalence was associated with per unit change in Der p 1  μ g/g (1.08, 95% CI 0.10–2.06) and Der 1  μ g/g (Der p1 + Der f1) (0.64, 95% CI 0.02–1.26). The change in having four or more attacks of asthma in the last 12 months was associated with per unit change in Der p 1  μ g/g (0.29, 95% CI −0.02 to 0.60) and Der 1  μ g/g (0.20, 95% CI 0.01–0.38). There was no effect for total Der p1 or Der f1 (total or μ g/g). Among children aged 6–7 yr, neither allergen was related to symptoms or severity prevalence. While our findings suggest that Dermatophagoides pteronyssinus may have a role in the primary causation of asthma, the complexity of this association reinforces the need for prospective studies.     

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.     

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.     

Comparison between serial skin-prick tests and specific serum immunoglobulin E to mite allergens

Sensitization to dust mite allergens can be determined by means of a skin-prick test (SPT) or by measurement of specific IgE antibodies in serum (sIgE). In our study, concordance of the results of both methods was analyzed on the basis of reproducible SPT results. Three consecutive SPTs were performed on 138 school children (age 6–8 years) at one-year intervals. SIgE was determined at the end of a two-year observation period. Seven common inhalant allergens (Dpt, Df, birch pollens, hazel pollens, grass pollens and cat and dog dander) were analyzed. The majority of subjects with positive SPT reactions to the respective allergen also showed sIgE (Dpt: 82/86; Df: 53/53; cat dander: 31/32; dog dander: 6/9; birch pollens: 29/31; hazel pollens: 22/22; grass pollens: 37/37). A significant correlation between the SPT [weal diameter (P₁) or allergen/histamine ratio (P₂)] and sIgE was found for Dpt (P₁ = 0.004/P₂ = 0.016), birch pollens (P₁ = 0.002/P₂ = 0.0001) and grass pollens (P₁ = 0.0005/P₂ = 0.0001). There was also a significant correlation between sIgE to Dpt and to either Der p 1 (p = 0.0001) or Der p 2 (p = 0.0001), as well as between sIgE of both major allergens (p = 0.0001). In the analysis of co-sensitization of Dpt and Df, most subjects sensitized to Dpt were also sensitized to Df (57/91). Children with sIgE to Dpt (n = 87) usually showed sIgE to Df (n = 83). In this study, SPT and sIgE results are concordant and appear equivalent when using reproducible SPTs. Therefore, in the case of a positive Dpt result, additional testing for sensitization to Df can be regarded as redundant when Dpt and Df are the major contributors to the allergen content of house dust.     

The interaction between early life upper respiratory tract infection and birth during the pollen season on rye-sensitized hay fever and ryegrass sensitization – a birth cohort study

Studies on early life viral respiratory infection and subsequent atopic disease in childhood have conflicting findings. Animal models show that viral respiratory infection in conjunction with allergen presentation can enhance sensitization. This prospective study assesses the influence of an upper respiratory tract infection (URI) in the first month of life and the season of birth on the development of hay fever and ryegrass allergen sensitization in childhood. From a Tasmanian cohort born during 1988 and 1989, a group of 498 children were followed up at 8 yr and another different group of 415 children were followed up at 16 yr. The ryegrass pollen season in Tasmania occurs in November and December. Forty‐four (9.6%) children in Follow‐up sample 1 and 47 (12.5%) children in Follow‐up sample 2 were born in the pollen season. The parental report of an early upper respiratory tract infection (EURI) was documented prospectively by a home interview at 1 month of age (median age 5.1 wk). Sensitization to ryegrass and house dust mite (HDM) was determined at 8 yr of age by skin prick testing and at 16 yr by ImmunoCap^®. Ryegrass sensitized hay fever was defined as a positive response to a question on hay fever plus the presence of ryegrass allergy. For children tested at age 8 and born in the pollen season, a EURI by postnatal interview was associated with an increased risk of ryegrass sensitization (OR 5.80 95% CI 1.07, 31.31) but not for children with a EURI born outside the pollen season (OR 0.62 95% CI 0.35, 1.08). Similarly, EURI was significantly associated with early onset (≤8 yr) ryegrass sensitized hay fever for children born in the pollen season (AOR 4.78 95% CI 1.17, 19.47) but was not associated with early onset ryegrass sensitized hay fever for children born outside the pollen season (AOR 0.76 95% CI 0.43, 1.33). These findings suggest that early life viral URI interacts with ryegrass allergen exposure in the development of ryegrass allergen sensitization and ryegrass sensitized hay fever symptoms.     

The prevalence of mouse allergen in inner‐city homes

Mouse allergen has not been studied in detail in the general population. It is common for patients from inner‐city environments to report significant mouse infestation in their homes and neighborhoods. The aim of this study was to determine the prevalence of mouse allergen in the homes of inner‐city children with asthma in relation to the demographic features of these children and their specific housing characteristics. Seventy‐eight dust samples from 39 inner‐city homes of Lodz, Poland, were analyzed for mouse allergen. Skin‐prick tests (SPTs) to mouse allergen were performed in all patients. In addition, data regarding the demographics and housing of the subjects were related to the mouse allergen levels. Mouse allergen was detected in 22 of 78 dust samples (28%), and in 18 of 39 homes (46%), including 13 kitchen (33%) and nine bedroom (23%) samples. Mouse allergen levels did not correlate between different rooms in the same home. The levels detected ranged from 0.09 to 2.34 µg/g of dust. The highest levels were found in kitchens, with median levels of 0.2 µg/g, 95% confidence interval (CI): 0.12–0.85 (range: 0.1–2.34 µg/g); in bedrooms the mean levels were 0.23 µg/g, 95% CI: 0.1–0.97 (range: 0.09–1.62 µg/g). Eleven of 18 children with detectable mouse allergen in house dust, and three of 21 without detectable mouse allergen in house dust, had a positive SPT to mouse allergen. On home inspection, 18% of the homes had evidence of mice in one or two rooms and had higher levels of mouse allergen (p < 0.01). None of the other subject or housing variables evaluated were associated with higher mouse allergen levels. In Polish children, mouse allergen is an important factor of sensitivity and should be recognized in the diagnosis of allergic diseases as well as in allergen‐reduction programmes.     

Exhaled nitric oxide in asthmatic and non-asthmatic children: Influence of type of allergen sensitization and exposure to tobacco smoke

Asthmatic bronchial inflammation is associated with increased nitric oxide concentrations in exhaled air (eNO). Recent data suggest that this effect arises from atopy. Our aim in this study was to find out whether atopy and sensitization to particular allergens influences eNO levels. A total of 213 subjects (41 asthmatics and 172 controls) (96 boys and 117 girls, 7.3–14 years of age) were studied. Parents completed a questionnaire that sought information on their children's respiratory symptoms and exposure to tobacco smoke. Subjects underwent skin‐prick tests for the following common allergens: Dermatophagoides pteronyssinus (Dpt), cat fur, Aspergillus fumigatus, Alternaria tenuis, mixed grass, mixed tree pollen, Parietaria officinalis, egg, and cow's milk. eNO was collected in 1‐l mylar bags (exhaled pressure 10 cmH₂O, flow 58 ml/s) and analyzed by using chemiluminescence. Atopic and non‐atopic children without a history of chronic respiratory symptoms had a similar geometric mean eNO (atopics, n = 28, 11.2 p.p.b.; non‐atopics, n = 96, 10.0 p.p.b.; mean ratio 1.1, 95% confidence interval [CI]: 0.7–1.6). Conversely, atopic asthmatic subjects had significantly higher eNO values than non‐atopic asthmatic subjects (atopics, n = 25, 24.8 p.p.b.; non‐atopics, n = 16, 11.4 p.p.b.; mean ratio 2.2, 95% CI: 1.2–3.9, p= 0.000). In children with rhinitis alone (n = 15) and those with lower respiratory symptoms other than asthma (n = 33), eNO increased slightly, but not significantly, with atopy. eNO levels correlated significantly with Dpt wheal size (r = 0.51) as well with the wheal size for cat, mixed grass, and Parietaria officinalis (r = 0.30–0.29), and with the sum of all wheals (r = 0.47) (p= 0.000). Subjects sensitized only for Dpt (but not those subjects sensitized only for grass pollen or other allergens) showed significantly higher eNO levels than non‐atopic subjects (16.4 p.p.b. vs. 10.2 p.p.b., mean ratio 1.6, 95% CI: 1.1–2.3, p= 0.002). In asthmatic subjects, Dpt sensitization markedly increased eNO levels (Dpt‐sensitized subjects: 28.0 p.p.b.; Dpt‐unsensitized subjects: 12.2 p.p.b.; mean ratio 2.3, 95% CI: 1.5–3.5, p= 0.000). Non‐asthmatic Dpt‐sensitized subjects also had significantly higher eNO values than non‐asthmatic, non‐Dpt‐sensitized subjects (14.2 p.p.b. vs. 10.1 p.p.b.; mean ratio 1.4, 95% CI: 1.1–1.9, p= 0.008). No difference was found between eNO levels in asthmatic subjects and control subjects exposed or unexposed to tobacco smoke. In conclusion, eNO concentrations are high in atopic asthmatic children and particularly high in atopic asthmatics who are sensitized to house‐dust mite allergen.     

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.     

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.