Influence of mattress characteristics on house dust mite allergen concentration

BACKGROUND: Exposure to a high level of house dust mite allergens (HDMAs) is considered as a risk factor for HDM sensitization and development of asthma in genetically disposed people. Mattresses are one of the most important sources of HDMA in people's living environment. OBJECTIVE: The aim of this study was to evaluate the association between mattress characteristics and HDMA concentrations on mattresses. METHODS: Dust samples of mattress surfaces were taken to evaluate the level of Der p 1 allergen. All participants filled in a questionnaire about the type of mattress, the type of covering (upper layer) of the mattress, dwelling characteristics and cleaning habits. Humidity and temperature of the bedroom were measured at the time of dust sampling. RESULTS: One hundred and sixty-eight questionnaires were filled in. Synthetic upper layer of the mattress was associated with a higher level of Der p 1 compared with cotton upper layer (2.6 vs. 0.8 microg/g Der p 1). Moreover, higher relative humidity (RH) was associated with significant higher concentrations and density of Der p 1. CONCLUSIONS: Two factors were associated with lower levels of Der p 1 found on mattresses, namely: a cotton upper layer of the mattress compared with a layer of synthetic material and lower RH at the time of sampling. As far as we know, the association between type of upper layer and concentration of Der p 1 has not been described before and could lead to the formulation of practical advices in order to reduce HDMA concentrations on mattresses.     

Blood histamine levels in cotton-dust exposed workers in a textile mill of Ahmedabad

Blood histamine levels were measured by the bioassay of histamine (on an isolated strip of guinea pig ileum) in workers exposed to cotton dust in a textile mill in Ahmedabad. Byssinotic subjects showed very high levels of blood histamine as compared to nonbyssinotic and control subjects. The blood histamine levels were not well correlated to the dust concentrations or duration of exposure but rather to the day of the week (ie, first, second, third, etc., after weekend break) on which the samples were collected. The blood histamine levels were high on the first day of the work week, when byssinotics complained most of their symptoms.     

The decay of house dust mite allergens, Der p I and Der p II, under natural conditions

Background: Fluctuations in the level of mite allergens in domestic house dust are the result of changes in the balance between synthesis, removal and decay. Purely physical forces as well as enzymatic degradation, mediated by house dust inhabiting microbes, may contribute to the decay of allergens in domestic dust. Knowledge about the speed of decay is essential for an understanding of the dynamics of allergen levels. Objective: The present study is a quantitative assessment of the speed of decay at nine combinations of temperature (15°C, 20°C and 25°C) and relative humidity (33%, 55% and 75%). Methods: Samples of mite infested material of an old rug were stored at these temperature/relative humidity-combinations for 6, 12 or 18 months, after the mites were killed by cither a freezing treatment or an acaricide (lindane). The microbes living in the rug presumably survive these treatments. Concentrations of Der p I and Der p II + Der f II. in extracts of the rug material, were measured by a radio immunoassay. Results: No significant changes in the levels of Der p I and Der p II +Der f II, could be detected even after 1¹/₂ year at a high temperature and humidity. Conclusion: These findings incidate that mite allergens can be extremely stable under normal domestic circumstances.     

Assessment of sublingual immunotherapy efficacy in children with house dust mite-induced allergic asthma optimally controlled by pharmacologic treatment and mite-avoidance measures

Although several studies have demonstrated the efficacy of subcutaneous immunotherapy in allergic asthma, few have shown the same benefit using sublingual immunotherapy (SLIT) in asthmatic patients. This study was conducted to assess the efficacy of house dust mite (HDM) SLIT in addition to allergen avoidance and standard pharmacologic treatment. A double-blind, placebo-controlled trial was performed in 111 children (aged 5-15 yr) with HDM-induced mild-to-moderate asthma. After a 4-week baseline phase, patients were randomly assigned to receive SLIT with tablets of HDM extract (n = 55) or placebo (n = 56) for 18 months. Pharmacologic treatment was adjusted every 3 months following a step-down approach. Asthma symptom scores, reduction in use of inhaled corticosteroids and inhaled beta(2)-agonists, rhinitis symptoms, lung function tests, skin sensitivity to HDM, dust mite-specific immunoglobulin (Ig) E and IgG(4), and quality of life (QoL) were assessed during the study. After 18 months of treatment, diurnal and nocturnal asthma symptoms scores did not show significant differences between SLIT and placebo groups. Inhaled corticosteroids and inhaled beta(2)-agonists use was reduced in both groups without significant differences between groups. There were no significant differences in lung function (forced expiratory volume in 1 s and peak flow rate variations) between groups. Rhinitis symptom score decreased in both groups, with no difference between the two groups. The severity dimension of QoL was significantly improved in the SLIT group (age 6-12 yr). SLIT induced a significant reduction of skin sensitivity to HDM (p < 0.01) and a significant increase in HDM-specific IgE and IgG(4) antibodies (p < 0.001) in the SLIT group compared with the placebo group. SLIT was well tolerated with mild/moderate local adverse events. No severe systemic reactions were reported. This study indicates that, when mild-moderate asthmatic children are optimally controlled by pharmacologic treatment and HDM avoidance, SLIT does not provide additional benefit, despite a significant reduction in allergic response to HDM. Under such conditions, only a complete, but ethically unfeasible, discontinuation of inhaled corticosteroid would have demonstrated a possible benefit of SLIT.     

An association between plastic mattress covers and sheepskin underbedding use in infancy and house dust mite sensitization in childhood: a prospective study

BACKGROUND: Higher house dust mite (HDM) allergen exposure during infancy has been associated with increased HDM sensitization. Infant bedding has been associated with the accumulation of varying levels of HDM. Prospective data on the relationship between infant bedding and the development of HDM sensitization has not been previously examined. OBJECTIVES: To determine if particular types of bedding used in infancy are associated with increased risk of house dust mite sensitization in childhood. METHODS: A population-based sample (n = 498) of children born in 1988 or 1989, and who were resident in Northern Tasmania in 1997, participated in this study. These children were part of a birth cohort study (1988-95), the Tasmanian Infant Health Survey. Data on infant underbedding and mattresses was available on 460 and 457 children, respectively. The main outcome measure was HDM sensitization defined as a skin prick test (SPT) reaction of 3 mm or more to the allergens of Dermatophagoides pteronyssinus and/or Dermatophagoides farinae. RESULTS: The use of either sheepskin underbedding or plastic mattress covers in infancy was associated with an increased risk of sensitization to HDM allergens at age 8 years. The adjusted risk ratio (RR) for sensitization to HDM with sheepskin in infancy was 2.27 (95% CI: 1.14, 4.55), P = 0.020. The adjusted RR for sensitization to HDM with the use of plastic mattress covers in infancy was 2.06 (95% CI: 1.22, 3.51), P = 0.007. The use of a foam mattress in infancy was not related to subsequent HDM sensitization. CONCLUSION: Infant's bedding plays a role in the development of HDM sensitization in childhood. Intervention studies to examine mite allergen levels and the role of underbedding on the development of HDM sensitization are required.     

Polyclonal and allergen-induced cytokine responses in children with elevated immunoglobulin E but no atopic disease

BACKGROUND: Reduced Th1 and elevated Th2 cytokine responses are considered to be a principal mechanism in the generation of the inflammation leading to the manifestations of atopic disease in the skin of atopic dermatitis and in the airways of asthma. If reduced Th1 and elevated Th2 responses are principal determinants of the manifestation of atopic disease it might be expected that subjects with established disease would exhibit differences in their cytokine profiles as compared with atopic patients without clinical disease. OBJECTIVE: To determine whether asymptomatic atopic children exhibit a cytokine imbalance similar to that seen in patients with established atopic disease or if they behave like non-atopic controls. Cytokine responses in a group of children with elevated IgE but no clinical manifestations of disease, atopic children with established disease and non-atopic controls were compared. METHODS: We examined allergen-induced (house dust mite, HDM, rye grass pollen and RYE) cytokine responses in parallel with polyclonal (staphylococcal enterotoxin B, SEB) cytokine responses in a group of children with elevated serum IgE levels without current or past evidence of atopic disease (median age 6.6 years) and compared these with a non-atopic control group (median age 6.5 years) and a group of children with atopic disease (median age 6.7 years). RESULTS: Symptomatic atopic children had reduced SEB-induced IFN-gamma and increased SEB-induced IL-4 and IL-5 as compared with non-atopic controls. In contrast, SEB-induced IFN-gamma, IL-4 and IL-5 production in asymptomatic atopics was not significantly different from the non-atopic control subjects. Allergen-induced Th1 (IFN-gamma) and Th2 (IL-5 and IL-13) cytokine production was increased in both symptomatic atopics and asymptomatic atopics when compared with non-atopic controls. CONCLUSION: The defect in polyclonally induced IFN-gamma production was associated with the clinical manifestation of atopic disease but not the atopic stateper se. This suggests that the global reduction in IFN-gamma is the key determinant of the development of overt atopic disease. In contrast, elevated allergen-induced Th2 cytokine responses in children related to the atopic state per se irrespective of the presence of clinical atopic disease.     

Personal exposure to house dust mite allergen in bed: nasal air sampling and reservoir allergen levels

BACKGROUND: Assessment of personal exposure to dust mite allergen has relied on proxy measures. Only recently has a means to directly measure inhaled allergen particle number become available (the intra-nasal air sampler). OBJECTIVE: To quantify inspired dust mite group 1 and group 2 allergen-bearing particles in bed in undisturbed conditions prior to sleep by nasal air sampling and to investigate the relationship between inhaled particles and reservoir allergen levels. METHODS: Twelve volunteers wore nasal samplers in bed for 6 evenings, nose-breathing in undisturbed conditions. Allergen-bearing particles ('halos') were detected by immunostaining for Der p 1, Der p 2, or Der p 1 and Der p 2 together, and counted by light microscopy. Count data were square root transformed for analysis of variance. Mattress dust samples were assayed for Der p 1 and Der p 2 concentrations. RESULTS: Square root detransformed mean particle counts per 30-min sample were: Der p 1, 4.22; Der p 2, 5.9; Der p 1 + Der p 2, 4.87; and for all samples, 5.01, with no difference between the groups. With replicate samples, halo number correlated significantly with mattress allergen concentrations (Der p 1 r = 0.80, P < 0.01; Der p 2 r = 0.68, P < 0.02). CONCLUSION: Nasal air sampling can be used to quantify nocturnal Der p exposure in undisturbed conditions in an area with moderate exposure to mite allergen and can provide a direct measure of inhaled mite allergen. The choice of either Der p 1 or Der p 2 is appropriate for this purpose.     

The effect of corona discharge on Der p 1

BACKGROUND: Reduction of house dust mite allergens in the domestic environment can play an important part in reducing sensitization and in the amelioration of symptoms in atopic individuals. Chemical and physical methods have been tried with varied levels of success. The present paper presents a novel electrostatic way of destroying Der p 1, the major mite allergen. OBJECTIVE: To assess the efficacy of negative Trichel, negative continuous glow, positive pulse and positive continuous glow corona in destroying Der p 1. To determine whether ozone has any effect on the integrity of Der p 1 in the experimental conditions present. METHODS: A simple point-to-plane apparatus was used to irradiate samples of Der p 1 for periods of 1, 15, 30, 45, 60, 120, 180, 240 and 300 min. Controls were exposed to the atmosphere with no corona products present for the equivalent time. The effect of the corona by-product ozone was investigated alone by exposing samples of Der p 1 to molecular ozone for 60 min. Der p 1 concentration was quantified by two-site monoclonal antibody ELISA. RESULTS: High current negative glow resulted in a 67.37% reduction in Der p 1 concentration after 300 min compared with a 50.5% reduction from a low current Trichel regime. High current positive glow corona gave a reduction of 25.22% while a low current positive pulse corona caused a 13.72% reduction after 300 min. All these reductions were statistically significant (P < 0.05) compared with unexposed controls. Negative corona always gave greater percentage reductions in Der p 1 concentration for each time exposure investigated. The pattern of percentage reduction follows an exponential rise to maximum relationship in respect to time. Samples of Der p 1 were not affected by exposure to molecular ozone. CONCLUSION: These data indicate corona products to be a powerful new method of destroying Der p 1 allergen that is not dependent on the presence of the oxidizing corona product ozone.     

Effect of mite-impermeable mattress encasings and an educational package on the development of allergies in a multinational randomized, controlled birth-cohort study – 24 months results of the Study of Prevention of Allergy in Children in Europe

BACKGROUND: Sensitization to house dust mite (HDM) is an important risk factor for the development of asthma and allergic disease in childhood. Higher levels of HDM allergen are linked to increased sensitization to HDM. OBJECTIVE: To study the effect of mite-impermeable mattress encasings and an educational package on the development of allergies in a newborn cohort. METHODS: Six hundred and ninety-six newborns at high risk of developing allergies were enrolled in three European countries (Germany, Austria, UK) in a prospective, randomized, controlled birth-cohort study. Children were randomly assigned to an intervention and control group. Intervention measures included the use of mite-impermeable mattress encasings for the child's bed and a simple educational package on allergen avoidance. The control group received basic information about allergies. Children were followed up at age 6, 12, 18 and 24 months. RESULTS: 80.9% of the children were followed up to the age of 24 months. No difference in the prevalence of sensitization to HDM (control vs. intervention group: 8.4% vs. 6.1%, P=0.33) or the development of symptoms (recurrent wheezing 10.3% vs. 10.7%, nocturnal cough 12.5% vs. 12.5%) or allergic diseases (asthma 3.5% vs. 5.1%, eczema 20.0% vs. 19.6%, rhinitis 28.9% vs. 25.8%) could be found between the control and intervention group. CONCLUSION: In this study, HDM avoidance did not show a protective effect on the development of sensitization to HDM or symptomatic allergy in children at age 24 months.