House dust mite allergen accumulation on sheepskins

AIM: Sheepskins, which are often used as infant bedding in New Zealand, are known to harbour large quantities of house dust mites and their allergens. In this study we determined the rate of accumulation of the house dust mite allergen, Der p 1 on new sheepskins, and the effects of washing and dry cleaning on its removal. METHODS: New sheepskins were placed on living-room floors (n = 6) and mattresses (n = 6) in six domestic dwellings in Wellington. Sheepskin dust samples were collected by vacuuming before placement, and at two, four and six weeks, after which they were warm-washed. They were replaced for a further six weeks, then dry-cleaned. Dust samples were collected before and after washing and dry-cleaning, and from mattresses and living-room floors. Dust samples were analysed for Der p 1 by double monoclonal antibody ELISA. RESULTS: Der p 1 levels rapidly increased in sheepskins placed on living-room floors and mattresses to a geometric mean level (range) of 9.0 micrograms/g (1.1-102.2) and 29.4 micrograms/g (5.3-131.1) at six weeks, respectively. After warm-water washing and replacement for a further six weeks, these levels were higher at 75.5 micrograms/g (50.1-260.4) and 31.9 micrograms/g (11.1-75.2), respectively. Sheepskin Der p 1 accumulation correlated with mattress (r = 0.78), and living-room floor Der p 1 levels (r = 0.94). Warm water washing and dry-cleaning reduced sheepskins Der p 1 levels by a mean of 79.2% and 95.3%, respectively. CONCLUSIONS: Sheepskins rapidly accumulate house dust mite allergens from the domestic environment. Due to very high levels and rapid accumulation of Der p 1, sheepskins as infant bedding should be discouraged for infants at risk of sensitisation to house dust mites. If they are to be used then it is important that they are washed or dry-cleaned regularly.     

Allergen content in dust from homes and schools in northern Norway in relation to sensitization and allergy symptoms in schoolchildren

BACKGROUND: Previous studies have shown a high prevalence of atopic diseases among school children in the community of S?r-Varanger. Moreover, animal dander followed by pollen and house dust mite, were the most common allergens in skin prick tests. OBJECTIVE: To assess the allergen content in homes (living-rooms and mattresses) and classrooms of children living in an arctic area at 70 degrees. The presence of allergens in homes and schools and their relationship to atopy was of particular interest. METHODS: Dust samples from 38 homes and seven schools in northern Norway were collected by vacuum cleaning. The presence of allergens of dog, birch, timothy, Cladosporium herbarum, codfish and hen egg-white was investigated by radio-allergosorbent test (RAST) inhibition and the presence of major allergens of cat Felis domesticus (Fel d I) and house dust mites (HDM) Dermatophagoides pteronyssinus (Der p I) and Dermatophagoides farinae (Der f I) by enzyme-linked immunosorbent assay (ELISA). RESULTS: Mattresses contained significantly more dust per unit area than living-rooms and classrooms. No statistically significant differences in allergen content for dog, birch, timothy. Cladosporium, codfish and hen egg-white were seen between HDM-sensitized and non-atopic children. Most dust samples contained dog allergens with the highest allergenic activity found in living-rooms of those keeping dogs. An increased level of Fel d I was detected in only one of 38 samples from living-rooms (this family kept a cat) and in 25 of 38 samples from mattresses with ranges from 24 to 84 ng/m2. The highest concentrations were found in mattresses of children keeping cats. Increased levels (> or = 25 ng/m2) of Der p I were found only in homes and virtually only in mattresses of HDM-sensitized children. An increased level of Der f I was found in only one case, i.e. in the mattress of an HDM-sensitized child where additionally Der p I and HDMs were demonstrated microscopically. When relating Der p I to HDM-sensitization an odds ratio of more than 16 (95% CI: 1.6-394.3) was found. All extracts from living-rooms included codfish allergens. Low RAST inhibition values were detected for hen egg-white. Cladosporium, birch and timothy pollen in most samples. Furthermore, the study demonstrated that dust from schools was relatively free of allergens. CONCLUSION: Previous findings indicating that the main allergen exposure problem in this geographical area is that of pet allergens were confirmed.     

Prevalence and determinants of house dust mite allergen in East German homes

BACKGROUND: In 1990/91, allergic sensitization to house dust mites (HDM) and other allergens was more prevalent in children from West Germany than from East Germany. OBJECTIVE: To test the hypothesis that low indoor exposure to HDM allergen in East Germany has contributed to this difference. METHODS: HDM allergen concentrations were determined in 634 East German dwellings shortly after the German reunification. RESULTS: HDM group I allergen (Der p 1 + Der f 1) levels in mattresses (median 2.16, geometric mean 2.07, maximum 278.9 microg/g dust) and carpets (median 0.41, geometric mean 0.48, maximum 96.3 microg/g dust) were within the range of levels determined in West Germany in other studies. One particular East German type of dwelling (light concrete buildings) was associated with lower mite allergen exposure, but only a minority of the population lived there. Coal heating, installed in the majority of dwellings before 1989, was associated with higher allergen exposure. Higher relative humidity (RH) was a main risk factor for higher Der p 1 exposure (odds ratio [OR] for exposure to > 0.05 microg/g dust on carpets: 1.4 [95% confidence interval (CI) 1.2-1.8] for + 10% RH) but not for higher Der f 1 exposure. Higher temperature was associated with a lower risk for elevated Der p 1 levels (> 0.05 microg/g dust on carpets): OR 0.6 (95% CI 0.5-0.8) for + 2 degrees C. CONCLUSION: Mite allergen exposure is not lower in East Germany than in West Germany. The data does not support the hypothesis, that low HDM allergen exposure in East Germany is a cause for the lower prevalence of HDM sensitization in East German children.     

Induction of atopic dermatitis by inhalation of house dust mite

BACKGROUND: The pathogenetic role of house dust mite in atopic dermatitis remains controversial. Recent studies have shown that intensive epicutaneous contact of house dust mite allergen with premanipulated skin may induce dermatitis. It is, however, uncertain whether such conditions are met during natural contact with house dust mite. In the past, allergen inhalation has been suggested to induce exacerbation of atopic dermatitis. The aim of this study was to investigate whether dermatitis could be induced in patients with atopic dermatitis by inhalation of house dust mite. METHODS: Twenty patients with atopic dermatitis underwent bronchial provocations with house dust mite. Challenge tests were performed with four concentrations of a standardized house dust mite extract in a double-blind, randomized, placebo-controlled fashion. Spirometry was performed, and FEV1 was measured before and after each challenge dose. Changes in severity or localization of itching or erythema were recorded. RESULTS: In nine of 20 patients with atopic dermatitis bronchial challenge with house dust mite induced unequivocal skin symptoms after 1.5 to 17 hours. Pruritic erythematous lesions on noninvolved sites together with exacerbations of existing lesions were seen in three patients. Three patients had an exacerbation only, and three other patients had new lesions only. In eight of nine patients with house dust mite inhalation-induced dermatitis, skin symptoms were preceded by an early bronchial reaction. All patients with house dust mite-induced dermatitis had a history of asthma, and as a group they had a higher mean blood total IgE level compared with the "negative skin responders." One patient had pruritic erythema on the placebo challenge day, without a preceding bronchoconstrictive reaction. The number of patients who had a skin response on the house dust mite challenge day was significantly higher than the number of patients who had a skin response on the placebo day (p = 0.011 [Prescott's test]). CONCLUSIONS: The respiratory route may be relevant in the induction and exacerbation of dermatitis in a subset of patients with atopic dermatitis who have early bronchial reactions after house dust mite inhalation, a history of asthma, and an elevated blood total IgE level. Furthermore, these findings suggest a possible causal relationship between bronchial reactions and skin reactions.     

Infant respiratory symptoms in relation to mite allergen exposure

The relationship between the Dermatophagoides pteronyssinus (Der p) I content of house dust and the respiratory symptoms reported for young infants was studied. One hundred and four infants, aged 3-15 months, were selected during July-September 1993 through the Dutch postnatal health care service, using a short screening questionnaire to identify mothers with respiratory allergy to house dust and/or pets. Forty-eight were selected from this group of mothers ("high risk" infants) and 56 infants were selected when neither of the parents reported allergy or chronic respiratory symptoms ("low risk" infants). All homes were visited in October 1993. Dust samples were collected from the infant's mattress and from other places in the home, and the Der p I content was measured in dust extracts. The results indicate that on more than half of the mattresses, the Der p I level was over 2,000 ng.g-1, the level suggested to be associated with an increased risk of sensitization. Information on respiratory symptoms ("wheeze" and "prolonged cough") experienced since birth was obtained by questionnaire from one of the parents on the dust sampling day. The occurrence of respiratory symptoms in the infants appeared to be positively related to the Der p I concentration of the dust. Although no objective measurements of respiratory symptoms were available, the results of this study suggest that exposure to mite allergen in early life may lead to respiratory symptoms that are suggestive of airway obstruction in the first year of life.     

Hypersensitivity to mites and house dust

The paper deals with the current data on hypersensitivity to house dust allergens, particularly to house dust mite allergens. Hypersensitivity to house dust mites is more prevalent than hypersensitivity to any other allergen. Ecologic factors for mite survival are cited, particularly emphasizing the importance of air humidity. Over the last 50 years there have been several changes in construction and furnishing of houses in developed countries which fostered mite proliferation. Mite allergens are identified and cloned, monoclonal antibodies to these allergens are produced. There are methods for estimating mite allergen concentration in homes which made possible to investigate the relationship between mite allergen exposure and development of bronchial hyperreactivity. Various methods for mite allergen avoidance are developed and their efficacy is under investigation.     

The effect of dry heat on mite, cat, and dog allergens

BACKGROUND: Various techniques have been tried in an attempt to reduce allergen levels in homes. This study investigated the effect of dry heat on mite, cat, and dog allergens. METHODS: Samples (50 mg) of Dermatophagoides pteronyssinus and D. farinae cultures, and of house dust rich in the major cat and dog allergens Fel d 1 and Can f 1 were heated for 5, 10, 15, 30, and 60 min at 60 degrees, 80 degrees, 100 degrees, 120 degrees, and 140 degrees C. Control samples remained at room temperature. Extracts were assayed with the appropriate two-site mono- or mono/polyclonal sandwich ELISA. RESULTS: For Der p 1, the breakdown was proportional to temperature and heating time; after 30 min at 120 degrees C, allergen levels were reduced to < 1% of control. Der p 2 was more heat stable, requiring 140 degrees C for 30-60 min to achieve > 99% reduction. D. farinae groups 1 and 2 allergens showed results similar to those obtained with D. pteronyssinus. In contrast, Can f 1 and Fel d 1 were considerably more thermostable, with 50% and 70%, respectively, of allergen remaining after 60 min at 140 degrees C. CONCLUSIONS: The effect of dry heat on allergens increased with increasing time and temperature, cat and dog allergens demonstrating greater heat resistance than mite allergens. Dry heating methods may represent an alternative technique for removal of mite allergens; however, the greater stability of Fel d 1 and Can f 1 suggests that this procedure may not be appropriate for pet allergens.     

Transient sensitization to house-dust mites: a study on the influence of mite exposure and sex

This study aimed to evaluate the prognosis of a previous positive skin test to house-dust mites (HDM) in relation to environmental exposure. A total of 115 children, 50 from Stockholm and 65 from northern Sweden, all with a previous (average 2.5 years) positive Phazet (Pharmacia AB, Uppsala, Sweden) skin prick test (SPT) to extracts of Dermatophagoides pteronyssinus (Dpt) and/or D. farinae (Df) were included. Dust samples were collected from the children's mattresses, and the total (Dpt, Df, and D. microceras [Dm]) amount of major mite allergen was measured by ELISA (50 children) and expressed as microgram allergen per gram of dust, or was measured by microscopy (65 children). The results of microscopic mite counts were transformed to approximate allergen levels as 2 micrograms equals 100 mites per gram of dust. Of 115 originally SPT-positive children, only 48 (48%) remained positive at retest, while the majority (58%) were SPT negative after 2 years. Among the 67 converted children, 11 were still exposed to mite allergen, but only to low concentrations (only one converted child being exposed above the suggested threshold level [TLV] of 2 micrograms/g), compared to 15/48 children still SPT positive who were exposed above the TLV. This shows that continued mite exposure is a major risk factor (OR = 30, CI 4.8-184) for continued positive SPT to HDM. A minor risk factor for continued sensitization was sex, boys having a higher risk than girls (OR = 2.2, CI 1.0-4.8). In conclusion, a surprisingly high rate of SPT conversion occurred, mainly as a result of a favorable indoor environment with low exposure to HDM and, to a lesser degree, as a result of sex. The present results support the view that the risk level of exposure is 2 micrograms mite allergen per gram of dust.     

Filtration of airborne allergens in various households

The filtration system investigated in this study uses the thermic convection caused by radiators for the adsorption of airborne particles. The effect of this filtration system on the reduction of clinical symptoms of allergic bronchial asthma was tested as well as its capability in retaining airborne allergens, in particular those of the house dust mite Dermatophagoides pteronyssinus (D. pter.), which are responsible for this special kind of asthma. Dust samples were taken before and after the heating season in households of 36 persons with D. pter. caused asthma. Their mite content was investigated using mite flotation and direct microscopy, their guanine content using the Acarex-test. An allergen extract obtained from the filters was tested on its allergen content by RAST-inhibition. It could be observed that compared to the preceding heating season 55% of the volunteers felt an improvement of their asthmatic symptoms. It was possible to extract allergens of D. pteronyssinus, house dust and mould from the filters. All these results show the capability of the filters to adsorb house dust mite (HDM) allergens.     

Japanese cedar pollinosis in children in our allergy clinic

Recently, it is pointed out that the incidence of Japanese cedar pollinosis has increased in children. We studied on the rate of sensitization and the onset of the disease in children under sixteen who visited allergy clinic in the Department of Otorhinolaryngology in Mie University Hospital. The percentage of positive rate of skin test and IgE antibodies of house dust mite was about 80 to 90% in 1981, 1991, and 1996. However, the percentage of positive rate of skin test and IgE antibodies of Japanese cedar pollen was 43% and 26%, respectively in 1981, but both increased to 58% in 1996. Most of Japanese cedar pollinosis patients also had house dust mite allergy. Among 115 pediatric patients who visited our allergy clinics in the past seven years, 32.2% were allergic to house dust mite alone, 8.6% were allergic to Japanese cedar pollen alone, 40.9% were allergic to both, and 6.1% were allergic to house dust mite, Japanese cedar pollen, and orchard grass pollen. 68% of the total 115 patients were boys, but significantly more girls had the pollinosis. 17.4% of those who are sensitized to the pollen were asymptomatic during the pollen season. Thus, it was confirmed that the rate of children sensitized to the pollen has apparently increased for the past twenty years. We should take care of those children who are sensitized to the pollen but asymptomatic during the pollen season.     

Tertiary structure of the major house dust mite allergen Der p 2: sequential and structural homologies

Sensitization to indoor allergens, especially those of the house dust mite, is strongly correlated with the development of asthma. We report the tertiary structure of the major house dust mite allergen, Der p 2, determined by NMR methods. The structure of Der p 2 is a beta-barrel and is composed of two three-stranded antiparallel beta-pleated sheets. This arrangement of beta-strands is similar to the immunoglobulin fold with respect to the orientation of the two sheets and the interactions of the strands. However, the three-dimensional structure of Der p 2 aligns equivalently with a number of proteins from different families within the immunoglobulin superfamily. The structural homology with the highest significance score from analysis by DALI is to Der f 2. Although Der p 2 and Der f 2 are 87% identical in amino acid sequence, they align in three dimensions rather poorly (4.85 A RMSD; Z-score, 8.58). This unexpected finding is likely due to the different solution conditions used during structure determination by NMR for both proteins. While the structural comparisons did not elucidate a clear homologue for the function of Der p 2 in mites, we report that Der p 2 is sequentially homologous to esr16. This is a protein from moths that is expressed coincident with molting. Thus, this homology has important ramifications for the study of mite allergy. The structure of Der p 2 provides a useful tool in the design of recombinant immunotherapeutics for the group 2 allergens.     

Reduction of the mite-allergen reservoir within mattresses by vacuum-cleaning. A comparison of three vacuum-cleaning systems

Mattresses are considered to be the main source of house-dust-mite (HDM) allergen. This study aimed to investigate different types of vacuum cleaners for their ability to reduce this allergen reservoir. Three types of vacuum cleaners were examined: a conventional vacuum cleaner, a water-trap cleaner, and a central vacuum cleaner. Cut out pieces of mattresses were analyzed for content of mite allergen after vacuum-cleaning. Three polyester mattresses from the homes of three children were selected for the study. These three mattresses had earlier been found to be contaminated by group 1 HDM allergen (8-15 micrograms/g of dust). Each mattress was divided into three main sections, separated by a safety zone, and each main section was subdivided into four parts. The three main sections were cleaned by each vacuum-cleaning system. Pieces 2-cm-thick of the surface of the mattresses were cut out, and extracts were made to assess the amount of mite allergen still present after different intensities of vacuum-cleaning. A considerable reduction in the level of mite allergen was found after using all three of the vacuum-cleaning systems. Only 22% of the original mite-allergen reservoir remained after intense vacuum-cleaning. Since the number of mattresses in the investigation was low, and niche formations of group 1 HDM allergen within the mattresses were observed, the results must be interpreted with caution. Furthermore, allergen-producing living dust mites were not affected by this method. However, intense vacuum-cleaning seems to reduce considerably the level of the mattress-bound mite-allergen reservoir, a fact which may be important in mite-allergic and mite-exposed families.     

Intrathecal administration of p-hydroxymercuribenzoate or phosphoramidon/bestatin-combined induces antinociceptive effects through different opioid mechanisms

BACKGROUND: House dust mite is an important cause of bronchial asthma. Seasonal variation of environmental house dust mite allergen levels and the specific IgE antibody to house dust mite have been reported. OBJECTIVE: We studied the changes in IgG subclass antibodies to house dust mite associated with seasonal variation of house dust mite allergen levels in houses of mite-sensitive asthmatic patients. METHODS: In 14 mite-sensitive asthmatic patients, house dust mite allergen (Der f 1) contents in bedding were measured monthly, and IgG subclass antibodies to house dust mite, Dermatophagoides farinae (D. farinae), were determined by enzyme-linked immunosorbent assay (ELISA) every 3 months from July to December. RESULTS: The concentration of Der f 1 in dust from bedding reached maximum levels in August and September, and significantly decreased in November and December compared with August and September (P < .05). Levels of D. farinae-specific IgG4 antibodies significantly decreased in December compared with September (P < .05) with no statistically significant change between September and June (P > .05). Levels of D. farinae-specific IgG2 antibodies decreased significantly in December compared with June (P < .05). The levels of IgG1 and IgG3 antibodies to D. farinae showed no significant differences during the study period. CONCLUSION: These findings suggest that seasonal changes in natural exposure to house dust mite allergen might lead to concurrent changes in specific IgG4 antibodies to house dust mite in mite-sensitive asthmatic patients and each IgG subclass antibodies to house dust mite might have a different kinetics.     

Indoor environmental factors associated with house-dust-mite allergen (Der p 1) levels in south-eastern Australian houses

BACKGROUND: Eighty households in the Latrobe Valley, Victoria, Australia, were sampled for house-dust-mite allergen (Der p 1). Allergen levels vary greatly between houses within climate regions. The reasons for this are not well understood. METHODS: House-dust-mite allergen samples were collected on six occasions between March 1994 and February 1995. All participating households contained at least one child between 7 and 14 years with a total of 148 subjects, 53 of whom were asthmatic. A detailed house survey was performed during every sampling visit, and a dwelling questionnaire was completed. Relative humidity was measured at the time of sample collection. RESULTS: The median bed allergen level was 30 microg/g during the first sampling period. Significantly higher allergen levels were associated with wool bedding and inner-spring mattresses (P < 0.001). As estimated from a multiple linear regression model, up to 70% reduction in bed allergen levels may be achieved by avoiding wool bedding and inner-spring mattresses. Other risk factors for high allergen levels included high indoor relative humidity, presence of substantial visible mould growth, brick cladding, and concrete slab foundation of the house. CONCLUSIONS: Avoiding wool bedding and replacing inner-spring mattresses with foam could substantially reduce bed allergen levels.     

Perceptual organization in schizophrenia: utilization of the Gestalt principles

BACKGROUND: Allergen immunotherapy results in a number of changes in clinical, inflammatory, and immunologic parameters. However, the basis for the specificity of this form of therapy is unknown, especially in the context of changes in T- and B-lymphocyte function after desensitization to specific allergens. OBJECTIVE: This study was designed to determine the immunologic consequences of rush immunotherapy. METHODS: We studied 10 patients who had positive skin test responses to the house dust mite Dermatophagoides pteronyssinus (Dpt) and cat dander extract. Each received rush immunotherapy to mite, but not cat dander, over a 2- to 4-week period until maintenance was achieved. Patients were evaluated before and when maintenance was achieved for skin test and nasal reactivity to mite and cat dander; antibody levels to the allergen were monitored, as were lymphocyte proliferative responses and cytokine production. RESULTS: Rush immunotherapy to house dust mite resulted in a significant reduction in skin and nasal reactivity to mite allergen, but not to cat allergen, in 10 of 10 patients. This was accompanied by a rise in serum anti-Dpt IgE, whereas anti-cat IgE was not altered (7 of 7 patients). In seven of seven patients there was an increase in anti-Dpt IgG4 levels. T-cell proliferative responses to mite antigen were suppressed, and numbers of CD8+ T cells increased in frequency. There was a marked increase in interferon-gamma production, particularly by CD4+ T cells in 10 of 10 patients. The correlation between the increases in interferon-gamma production and the changes in cutaneous reactivity was highly significant. CONCLUSION: We show that rush immunotherapy is immunologically specific in eliciting changes in T- and B-cell responses to the desensitization antigen. The specificity and potential benefit of immunotherapy may be linked to the increase in interferon-gamma production by allergen-activated CD4+ T lymphocytes.     

Occupational allergy in greenhouse workers: sensitization to Tetranychus urticae

BACKGROUND: Tetranychus urticae (TU) is a macroscopic mite which is found infesting a large number of plants of economic interest. It has rarely been described as a cause of occupational allergic disease in agricultural workers. OBJECTIVE: To describe TU sensitization in greenhouse workers attending the outpatient allergy unit and its clinical associations, and to characterize the allergens involved. MATERIALS AND METHODS: Twenty-four consecutive carnation greenhouse workers with allergy-related symptoms, referred to our outpatient clinic during a 6-month period, were included. We made the diagnostic extract from carnation leaves heavily infested with TU. Skin-prick test, specific IgE measurement and bronchial provocation test with TU extract were carried out in all subjects. Allergen characterization was achieved by SDS-PAGE (sodium dodecylsulfate-polyacrylamide gel electrophoresis) and immunoblotting. RESULTS: Sixteen patients (66%) presented positive skin-prick test and specific IgE and were diagnosed allergic to TU. Fifteen patients suffered from bronchial asthma, 14 rhinitis and five urticaria. Twelve exhibited positive bronchial provocation test to the TU extract. On RAST-inhibition studies, there was no evidence of crossreactivity between TU extract and D. pteronyssinus. An allergen at 19 kDa was determined in the TU extract by SDS-PAGE immunoblotting studies. CONCLUSION: TU could be an important occupational allergen in greenhouse workers showing allergic symptomatology. There is no crossreactivity between this mite and the house dust mite D. pteronyssinus.     

Expression of Msx-2 during development, regeneration, and wound healing in axolotl limbs

BACKGROUND: High exposure to house dust mite allergen during the first year of life has been found to increase the risk of subsequent asthma and mite sensitization. Environmental factors, home construction and cleaning methods used are associated with levels of dust mites in the home. OBJECTIVE: To investigate determinants of levels of Der p 1 and Der f 1 mite allergens in homes of infants in southern Tasmania. METHODS: Dust samples were collected from 72 homes of infants participating in the Tasmanian Infant Health Survey (TIHS). The Der p 1 and Der f 1 allergen concentrations in these samples were measured. The TIHS interviewers obtained information from the mothers of the infants via a questionnaire, observed specified aspects of the home environment, and took readings of bedroom temperature and humidity. The effect of each item on allergen concentration in dust from bedroom floors was examined in a variety of ways. Those items which in this study appeared to be significantly related to allergen concentrations plus items which in other studies have been found to be related to allergen concentrations were then investigated further in multivariate models. RESULTS: Der p 1 allergen concentration (microg/g) and density (microg/m2) in dust from bedroom floors were found to be related to several home environment factors. In the univariate analyses, indoor humidity, 24 h maximum temperature, number of residents and a combination of floor covering and cleaning methods appeared to have a significant effect on allergen levels. These factors remained important in the multivariate model except that indicators for mould in the bathroom and drying washing on an outside line replaced indoor humidity. CONCLUSION: Features related to home dampness, the number of residents and floor covering and cleaning were major determinants of Der p 1 levels in the bedrooms studied.     

Prevalence and distribution of indoor allergens in Singapore

BACKGROUND AND AIMS: Immediate hypersensitivity to indoor allergens is known to be associated with allergic asthma. This study evaluated the prevalence and distribution of six indoor allergens in 956 dust samples obtained from homes, childcare centres, schools, and a hospital in tropical Singapore. Seasonality of mite allergens was also assessed. METHODS: The major allergens of the Dermatophagoides spp. dust mites, Der p 1 and Der f 1; major cat and dog allergens, Can f 1 (dog) and Fel d 1 (cat); and cockroach, Bla g 1, were measured by specific enzyme immunoassays. Allergen levels of the storage mite, Blomia tropicalis (Blo t), were measured by a fluorescent allergosorbent test (FAST) inhibition assay. RESULTS: Our results showed that homes had significantly higher concentrations and prevalence of allergens compared with the other locations, except for Bla g 1, where higher mean levels were found in schools. Within the homes, the highest concentrations of mite allergens were found in mattresses (geometric mean: 1.2 microg/g dust Der p 1; 2717 Allergen Units per gram dust [AU/g] Blo t), and carpets (1.5 microg/g Der p 1; 1620 AU/g Blo t), whilst Bla g 1 was mainly concentrated in the storerooms (geometric mean = 3.5 units/g) and kitchens (geometric mean = 5.1 units/g). The major cat and dog allergens were well distributed and not confined to homes with pets. Their highest levels were found in dust of soft furnishings, carpets and mattresses. There was an absence of significant seasonal variation in Der p 1, Der f 1 and Blo t levels in the homes over a 1 year period. CONCLUSION: The results indicate that compared with public places, the home consitutes a major reservior of indoor allergens. Allergens of the storage mite, B. tropicalis, should be considered as a major allergenic component of dust in Singapore.     

Higher asthma occurrence in an urban than a suburban area: role of house dust mite skin allergy

Understanding of geographical differences in asthma prevalence may be helpful in explaining recent increases in the occurrence of asthma. We wondered whether differences in allergic sensitization or other factors could explain differences in reported occurrence of asthma between an urban centre and a neighbouring suburban area. From the European Community Respiratory Health Survey (ECRHS) questionnaire, responses on asthma symptoms and risk factors and results of 11 skin allergy tests were available from 656 young adults living in urban or south suburban Antwerp, Belgium. Answers to five asthma questions were selected as dependent variables, and eight personal or environmental risk factors, as well as house dust mite (HDM) allergy, as independent variables. The effect of each independent variable on the association of asthma variables with area was assessed. Prior asthma diagnosis, present asthma symptoms, the selected risk factors and HDM allergy were all more frequently recorded in urban Antwerp. Difference in HDM allergy accounted for most of the difference in prior (mostly childhood) asthma diagnosis, since correction for it decreased the odds ratio from 2.10 to 1.65. On the contrary, the regional differences in recent asthma symptoms were not explained by HDM allergy differences nor by any other factor under study. This urban-suburban comparison indicated that house dust mite allergy is a major determinant of prior (childhood) asthma, whereas factors contributing to higher urban prevalence of present asthma symptoms could not be identified. Furthermore, our results indicate that it may be inappropriate to combine data from neighbouring areas, when their similarity has not been verified.     

Specific IgA and IgG antibodies to house dust mite Dermatophagoides farinae in nasal secretions

As far as we know, IgA and IgG antibodies to purified house dust mite allergens Der fI and Der fII in nasal secretions have never been documented. Therefore, we determined specific IgA, SIgA and IgG antibodies (abs) to crude extract of D. farinae and its purified allergens Der fI and der f II in nasal secretions collected by aspiration from 34 normal subjects, 25 untreated nasal allergic patients and 28 treated nasal allergic patients on parenteral immunotherapy by means of an avidin-biotin ELISA. The following results were obtained. (1) The specific IgA, SIgA and IgG abs to each of the three kinds of allergens correlated with each other. The groups of patients with nasal allergy (both treated and untreated) showed higher levels of specific IgA, SIgA and IgG abs to the allergens than the normal group. (2) In the group of treated patients, the levels of specific abs were not correlated with the clinical improvement of symptoms or the degree of response to nasal challenge. (3) The treated patients failed to show significantly higher levels of abs in nasal secretions than the untreated patients. (4) The specific IgA and SIgA abs in nasal secretions seemed to be predominantly produced locally, and IgG abs might be transudated from the circulation.