A combined approach to reduce mite allergen in the bedroom

House Dust Mite Related Allergic Rhinitis and REM Sleep Disturbances

PURPOSE

Sleep disturbances are common in patients with allergic rhinitis (AR). Perennial allergens like house dust mites (HDM) are difficult to avoid and have nocturnal impacts on the respiratory system and Quality of Life (QOL). The Rapid Eye Movement (REM) sleep stage is associated with memory, cognition, dreams, and overall restfulness, which can be impaired in AR patients with Sleep Disordered Breathing (SDB) even when normal all-night apnea-hypopnea (AHI) or respiratory disturbance (RDI) indices are noted on polysomnography (PSG). We hypothesized that AR HDM allergen positive patients would show REM-specific SDB reflected in their objectively elevated REM-RDI values.

MATERIALS AND METHODS

This retrospective analysis of 100 patients included 47 with HDM positive allergy testing. All patients underwent PSG testing calculating the RDI during REM. Multivariate logistic regression models evaluated relationships between allergic statuses and sleep parameters while controlling for potential confounders.

RESULTS

Compared with allergy negative patients, HDM allergen positive patients were significantly more likely (OR 4.29, 95%CI 1.26-14.62) to have a REM-RDI in the moderate/severe range (≥15 events/h).

CONCLUSIONS

Our study highlighted the significance of respiratory allergies to HDM in patients with SDB. We revealed a significant relationship between HDM allergen positivity and SDB characterized by elevated REM-RDI regardless of all-night AHI, RDI, or REM-AHI values. Clinical implications of knowing about disturbed REM and/or HDM allergenicity include better preparation, treatment, outcomes, and QOL for allergic, SDB, and upper airway surgery patients.

House dust mite control measures for asthma

EDITORIAL NOTE

This 2011 review predates current reporting standards and methodological expectations for Cochrane Reviews. It should not be used for clinical decision‐making.

BACKGROUND

The major allergen in house dust comes from mites. Chemical, physical and combined methods of reducing mite allergen levels are intended to reduce asthma symptoms in people who are sensitive to house dust mites.

OBJECTIVES

To assess the effects of reducing exposure to house dust mite antigens in the homes of people with mite-sensitive asthma.

SEARCH STRATEGY

PubMed and The Cochrane Library (last searches Nov 2007), reference lists.

SELECTION CRITERIA

Randomised trials of mite control measures vs placebo or no treatment in people with asthma known to be sensitive to house dust mites.

DATA COLLECTION AND ANALYSIS

Two authors applied the trial inclusion criteria and evaluated the data. Trial authors were contacted to clarify information.

MAIN RESULTS

Fifty-four trials (3002 patients) were included. Thirty-six trials assessed physical methods (26 mattress encasings), 10 chemical methods, and 8 a combination of chemical and physical methods. Despite the fact that many trials were of poor quality and would be expected to exaggerate the reported effect, we did not find an effect of the interventions. For the most frequently reported outcome, peak flow in the morning (1565 patients), the standardised mean difference was 0.00 (95% confidence interval (CI) -0.10 to 0.10). There were no statistically significant differences either in number of patients improved (relative risk 1.01, 95% CI 0.80 to 1.27), asthma symptom scores (standardised mean difference -0.04, 95% CI -0.15 to 0.07), or in medication usage (standardised mean difference -0.06, 95% CI -0.18 to 0.07).

AUTHORS' CONCLUSIONS

Chemical and physical methods aimed at reducing exposure to house dust mite allergens cannot be recommended. It is doubtful whether further studies, similar to the ones in our review, are worthwhile. If other types of studies are considered, they should be methodologically rigorous and use other methods than those used so far, with careful monitoring of mite exposure and relevant clinical outcomes.

House dust mite control measures for asthma

BACKGROUND

The major allergen in house dust comes from mites. Chemical, physical and combined methods of reducing mite allergen levels are intended to reduce asthma symptoms in people who are sensitive to house dust mites.

OBJECTIVES

To assess the effects of reducing exposure to house dust mite antigens in the homes of people with mite-sensitive asthma.

SEARCH STRATEGY

Cochrane Airways Group trials register, and PubMed and The Cochrane Library (last searches June 2004), reference lists.

SELECTION CRITERIA

Randomised trials of mite control measures vs placebo or no treatment in asthmatic people known to be sensitive to house dust mites.

DATA COLLECTION AND ANALYSIS

Two reviewers applied the trial inclusion criteria, assessed their quality and extracted the data independently. Study authors were contacted to clarify information.

MAIN RESULTS

Forty-nine trials (2733 patients) were included; the number of patients has more than doubled since the last version of this review. Thirty-one trials assessed physical methods, ten assessed chemical methods, and eight a combination of chemical and physical methods. Despite the fact that many trials were of poor quality and would be expected to exaggerate the reported effect, we did not find an effect of the interventions. For the most frequently reported outcome, peak flow in the morning (1339 patients), the standardised mean difference was -0.02 (95% confidence interval (CI) -0.13 to 0.08). There were no statistically significant differences either in number of patients improved (relative risk 1.01, 95% CI 0.80 to 1.27), asthma symptom scores (standardised mean difference -0.01, 95% CI -0.10 to 0.13), or in medication usage (standardised mean difference -0.05, 95% CI -0.18 to 0.09).

REVIEWERS' CONCLUSIONS

Chemical and physical methods aimed at reducing exposure to house dust mite allergens cannot be recommended. It is doubtful whether further studies, similar to the ones in our meta-analysis, are worthwhile. If other types of studies are considered, they should be methodologically rigorous and use other methods than those used so far, with careful monitoring of mite exposure and relevant clinical outcomes.

Allergic rhinitis due to house dust mites: evaluation of the efficacy of specific sublingual immunotherapy

BACKGROUND

The efficacy and safety of sublingual immunotherapy (SLIT) in patients with chronic rhinitis related to sensitization to house dust mites are still controversial.

METHODS

After application of an anti-mite mattress cover, patients were only included in the study when the cumulative symptom score over a fortnight was greater than 70 out of a possible total of 168. Thirty-two of the 120 patients selected were randomized to receive SLIT for 2 years: 17 received placebo and 15 received the Dermatophagoides pteronyssinus and D. farinae 50/50 allergen extract.

RESULTS

Significant between-group differences were observed after 1 year and persisted at the end of the second year for the rhinitis total score (P < 0.02), blocked nose score (P < 0.01) and nasal itching score (P < 0.01). Skin reactivity to house dust mites was significantly reduced in the group receiving house dust mite extract (P < 0.03). No statistical difference was observed between the two groups for medication scores, but a low medication consumption was observed in all patients. No serious and no systemic adverse reactions were reported.

CONCLUSION

This study indicates the superiority of active treatment vs. placebo, evaluated on efficacy criteria (rhinitis score) or objective criteria (skin reactivity). The availability of a solid form (tablet) could represent a progress in terms of patient acceptability.

A randomized controlled trial of mite allergen-impermeable bed covers in adult mite-sensitized asthmatics

BACKGROUND

Mite-allergic patients with allergic disease should benefit from avoiding mite allergens. Many physicians, however, are yet to be convinced that allergen avoidance can make a significant contribution to asthma management in these patients. Many allergen-avoidance regimes include multiple measures of allergen reduction, but as mite exposure in the home is most likely to be greatest in bed dust, bedding is usually the first target for intervention.

OBJECTIVE

This study selected adult patients considered to be most likely to benefit from avoiding mite allergens, namely diagnosed asthmatics, sensitized to house dust mites and exposed to mite allergen in their mattresses. Patients were randomized into a placebo-controlled trial of the use of allergen-impermeable bed covers for 12 months, without any other form of mite-reduction measures.

METHODS

Adults with asthma were selected from general practices and asthma clinics in south-east London. Their serum IgE to mite allergens and allergen content of mattress dust samples were measured. Those with >0.70 kU/L mite-specific IgE and >2 microg/g Der p 1 were randomized into active or placebo treatments. Information was collected on allergic symptoms and medication use and quarterly peak flow diaries were kept throughout the trial. Dog or cat allergic patients were excluded if they had a pet at home to which they were sensitized.

RESULTS

The mean decrease in microg/g Der p 1 was 25.7 (95% CI 8.9, 74.1) in the active group and 4.5 (95% CI 1.8, 11.5) in the placebo group. Der p 1 concentrations in the active and placebo groups at the end of the trial were not significantly different. There was no effect on peak flow or asthma symptoms in a simple comparison of the treatment and placebo groups.

CONCLUSION

In this group of patients, mite allergen avoidance in the bed by the use of allergen-impermeable bedding alone cannot be recommended as an effective way of relieving asthma symptoms.

House dust mite allergen in US beds: results from the First National Survey of Lead and Allergens in Housing

BACKGROUND

Although exposure to house dust mite allergen is a major risk factor for allergic sensitization and asthma, nationwide estimates of dust mite allergen levels in US homes have not been reported.

OBJECTIVE

The purpose of this study was to estimate the prevalence of dust mite allergen in beds of US homes and to identify predictors of dust mite allergen concentration.

METHODS

Data were obtained from the first National Survey of Lead and Allergens in Housing, a cross-sectional survey of 831 permanently occupied noninstitutional housing units that permitted resident children. Dust mite allergen concentration (Der f 1 plus Der p 1) was determined from a dust sample collected from a bed. The percentages of homes with concentrations at or greater than detection, 2.0 microg/g bed dust, and 10.0 microg/g bed dust were estimated. Independent predictors of allergen concentration were assessed with multivariable linear regression.

RESULTS

The percentages of US homes with dust mite allergen concentrations at or greater than detection, 2.0 microg/g, and 10.0 microg/g were 84.2% (SE, 1.73), 46.2% (SE, 2.0), and 24.2% (SE, 2.1), respectively. Independent predictors of higher levels were older homes, non-West census regions, single-family homes, no resident children, lower household income, heating sources other than forced air, musty or mildew odor, and higher bedroom humidity.

CONCLUSION

Most US homes have detectable levels of dust mite allergen in a bed. Levels previously associated with allergic sensitization and asthma are common in US bedrooms. Predictors can be used to identify conditions under which homes are more likely to have increased dust mite allergen levels.

Effect of mattress and pillow encasings on children with asthma and house dust mite allergy

BACKGROUND

House dust mite (HDM) allergy is a frequent cause of allergic asthma in children. Reduction of exposure seems to be the most logical way to treat these patients.

OBJECTIVE

Our aim was to investigate whether mattress and pillow encasings resulted in an effective long-term control of HDM allergen levels, thereby reducing the need for asthma medication in children with asthma and HDM allergy.

METHODS

In a prospective, double-blind, placebo-controlled study 60 children (age range, 6-15 years) with asthma and HDM allergy were randomized to active (allergy control) or placebo mattress and pillow encasings. After a 2-week baseline period, follow-up was performed every 3 months for 1 year. During the entire study period, the dose of inhaled steroids was tapered off to the lowest effective dose according to well-defined criteria.

RESULTS

Fifty-two patients completed the trial, and 5 were excluded, leaving data from 47 children (26 in the active treatment group and 21 in the placebo group) for analysis. A significant perennial reduction in HDM allergen concentrations was seen only for the active treatment group. Also, a significant decrease in the dose of inhaled steroids (mean, 408 to 227 microg/d; P <.001) was found for the active treatment group only, with significant differences between groups after 9 and 12 months. After 1 year, the dose of inhaled steroids was reduced by at least 50% in significantly more children in the active treatment group than in the placebo group (73% vs 24%, P <.01).

CONCLUSION

Encasing of mattresses and pillows resulted in a significant long-term reduction in HDM allergen concentrations in mattresses and in the need for inhaled steroids in children with asthma and HDM allergy.

Effect of mattress encasings on atopic dermatitis outcome measures in a double-blind, placebo-controlled study: the Dutch mite avoidance study

BACKGROUND

House dust mite (HDM) allergen might induce and maintain atopic dermatitis (AD). Reduction of allergen load by applying encasings might improve the clinical symptoms of AD.

OBJECTIVE

We sought to investigate, in a randomized, double-blind, placebo-controlled study, whether reducing HDM allergen levels by using mattress, duvet, and pillow encasings for 12 months will result in improvement in AD symptoms.

METHODS

Patients with AD (8-50 years old and allergic to HDM), having a Leicester sign score (a dermatitis score) of at least 1% extent and a severity score of 6 points or greater, were randomly allocated to an active (n = 45) or a placebo allergen-avoidance group (n = 41). Avoidance measures consisted of applying HDM-impermeable encasings for mattresses, pillows, and duvets for the active treatment group and cotton encasings for the placebo group. Effect on allergen concentrations (Der p 1 and Der p 1 plus Der f 1), Leicester sign score extent and severity, visual analogue scale scores for itching and sleeplessness, intradermal test results, atopy patch test results, total serum IgE levels, anti-Der p 1-specific IgE levels, and total blood eosinophil counts were studied.

RESULTS

The active encasings reduced the Der p 1 allergen concentration in the mattress after 12 months with a factor 2.1 (P =.007) and the Der p 1 plus Der f 1 allergen concentration with a factor of 2.5 (P =.005); no significant change in allergen concentrations in mattresses was seen in the placebo group. Although the decrease in allergen load was significant, no differences in treatment-induced changes were seen between the placebo and active groups.

CONCLUSIONS

Use of HDM-impermeable encasings resulted in a significant decrease in Der p 1 and Der p 1 plus Der f 1 allergen concentrations. However, this reduction in allergen load did not result in significant changes in clinical parameters between the groups. Reduction of allergens in other environments (work, school, and outdoors) might be equally important in improving symptoms of AD.

Clinical evaluation of the effect of anti-allergic mattress covers in patients with moderate to severe asthma and house dust mite allergy: a randomised double blind placebo controlled study

BACKGROUND

The use of anti-allergic mattress covers in patients with asthma can result in a large reduction in the level of house dust mite allergen in dust samples. Apart from a reduction in histamine induced bronchial hyperresponsiveness, there are few data on the effect of mattress covers on clinical efficacy and quality of life in patients with moderate to severe asthma.

METHODS

Thirty patients with asthma and house dust mite allergy were studied in a randomised, double blind, placebo controlled study. Before and after using anti-allergic covers for 1 year, dust was collected from the mattresses to determine concentrations of Dermatophagoides pteronyssinus (Der p 1), and bronchial hyperresponsiveness and quality of life were measured. The patients scored their symptoms (lungs and nose), morning and evening peak flow values, and rescue medication for 14 days before and after the intervention period.

RESULTS

There was a significant reduction in the concentration of Der p 1 in the dust collected from the mattresses in the actively treated group after 1 year compared with before treatment; no change was found in the placebo group. In both the actively treated and placebo groups there was no significant improvement in PC(20) histamine. Quality of life improved similarly in both groups. The symptom score of the lower airways did not significantly change in either group. A significant decrease in nasal symptom score was seen in the actively treated group compared with before treatment, but there was no significant difference between the groups. No changes in morning and evening peak flow values, peak flow variability, nor in the use of rescue medication were found in either group.

CONCLUSION

The use of anti-allergic mattress covers results in significant reductions in Der p 1 concentrations in carpet-free bedrooms. However, in patients with moderate to severe asthma, airways hyperresponsiveness and clinical parameters are not affected by this effective allergen avoidance.

The effect of anti-allergic mattress encasings on house dust mite-induced early- and late-airway reactions in asthmatic patients. A double-blind, placebo-controlled study

BACKGROUND

Anti-allergic mattress encasing may provide clinical benefit in asthmatic patients. However, the effect of mattress encasings on allergen-specific parameters, such as bronchial reactions to house dust mite (HDM) challenge, is not clear.

OBJECTIVE

To investigate the effect of anti-allergic mattress encasings on allergen sensitivity in patients with moderate to severe asthma.

METHODS

Twenty-seven patients with asthma and HDM allergy were studied in a double-blind, placebo-controlled study. Concentrations of Dermatophagoides pteronyssinus (Der p 1) were measured in mattress dust before and after 1 year of treatment; bronchial histamine challenge, bronchial challenge with HDM and intradermal skin challenges with HDM were performed. The number of eosinophils in peripheral blood was assessed.

RESULTS

In the active group, but not in the placebo group, there was a significant reduction in Der p 1 concentration in the dust collected from the mattresses after 1 year of treatment compared to before. There was a significant difference between the groups with respect to HDM-induced early-reaction (ER) in the airways and the number of blood eosinophils, which reflected an increase in ER and eosinophils in the placebo group without significant change in the active group. No significant improvement in PC20 histamine, late-reaction (LR) and skin tests was found in either groups.

CONCLUSION

Our data suggest that encasings protect against a further increase in allergen sensitivity in asthmatic patients, so their use should be recommended.

Domestic control of house dust mite allergen in children's beds

BACKGROUND

House dust mite allergen levels in humid coastal regions of Australia are high, particularly in beds. Because high allergen levels in beds are associated with more severe asthma, reduction of levels may be important for asthma control.

OBJECTIVE

We tested the effectiveness of an acaricidal treatment of bedding in combination with occlusive mattress and pillow encasings in reducing allergen levels in children's beds in a community setting.

METHODS

A total of 14 beds of children were selected for the active intervention. In each home the bed of a sibling of nearest age was selected as the control. Dust was vacuumed from beds by using a standard protocol, and Der p 1 levels were measured by using ELISA. Adjacent settling dust was collected by using opened Petri dishes. The intervention consisted of encasing mattresses and pillows in occlusive covers and washing all bedding with Acaril, an acaricidal additive. The acaricidal wash was repeated twice in 7 households at 2-month intervals. Control beds were not treated.

RESULTS

The mean Der p 1 concentration at baseline was 27.9 microg/g in the active beds and 18.1 microg/g in the control beds. At 4 days after intervention, Der p 1 decreased to 3.2 microg/g and 15.7 microg/g in active and control beds, respectively. The average difference (active minus control) over the first 8-week cycle was 78.5% (P <.0001), and the difference over 3 washing cycles was 125.1% (P <.05). The mean rate of settling Der p 1 adjacent to the actively treated beds decreased from 24.4 ng.m(-2).d(-1) at baseline to 10.0 ng.m(-2).d(-1) after intervention (P <.01).

CONCLUSION

A substantial reduction in Der p 1 levels in beds and in airborne dust in a humid region with naturally high house dust mite allergen levels can be achieved and sustained in a community setting with use of occlusive covers and a rigorous washing routine.

[Habitat of the allergic child: theory and practice]

Control of the asthmatic child's environment forms an integral part of therapeutic care. This requires knowing what the main allergens in the child's habitat are and how they arise: eg, acarids, animal teguments, insects and fungi. The overall measures for reducing them chiefly entail controlling humidity: regular airing, or even ventilation, and eliminating sources of humidity can be recommended. Control of acarids will require modifying furnishings (no mats or carpeting, non hangings or heavy curtains, a slatted not interior spring bed base). Acarid-repellent loose covers seem to be more effective than acaricides, which give conflicting results. Physical processes, although necessary, are seldom sufficient. Animals should be evicted. If this is impossible, certain measures have proved effective, however. Insects and moulds are controlled by specific sanitary measures. A practical approach is proposed that takes into account both theoretical demands and everyday realities.

House-dust-mite sublingual-swallow immunotherapy (SLIT) in perennial rhinitis: a double-blind, placebo-controlled study

BACKGROUND

The safety and efficacy of sublingual-swallow immunotherapy (SLIT) in rhinitis caused by house-dust mite were evaluated in a double-blind, placebo-controlled study including 75 patients for 24 months.

METHODS

Patients received either placebo or SLIT with a standardized Dermatophagoides pteronyssinus (D.pt.) - D. farinae (D.f) 50/50 extract. The mean cumulative dose was 90,000 IR, equivalent to 2.2 mg of Der p 1 and 1.7 mg of Der f I. Symptom and medication scores were assessed throughout the study. Exposure to house-dust mite, skin sensitivity, and serum specific IgE and IgG4 were assessed before starting treatment and after 12 and 24 months.

RESULTS

Seventy-two patients (36 active-36 placebo) were eligible for intent-to-treat analysis. Thirty-six patients dropped out of the study. The number of patients who dropped out due to lack of efficacy was eight out of 37 (21.6%) in the active treatment group compared to 15 out of 38 (39.5%) in the placebo group (chi-square=2.81, P=0.09). Total symptom and medication scores decreased significantly after 12 and 24 months (P<0.05) of treatment in both groups, but no significant difference was observed between the active and placebo groups. After 24 months, the number of patients with high levels of indoor allergenic load decreased significantly in both groups compared to baseline data (P=0.01). Specific IgE (D.pt. and D.f.) increased significantly in the active treatment group after 12 and 24 months, while no change was observed in the placebo group. Specific IgG4 levels were not significantly modified in either group. Two patients in each group reported mild adverse effects. No severe adverse effects were reported.

CONCLUSIONS

We conclude that SLIT in rhinitis caused by house-dust mite was safe, but there was a lack of consistent clinical benefit compared to placebo, probably due to the impact of the allergen avoidance measures that lowered the allergen burden.

Effects of house dust mite avoidance measures on Der p 1 concentrations and clinical condition of mild adult house dust mite-allergic asthmatic patients, using no inhaled steroids

BACKGROUND

Exposure to house dust mite (HDM) allergens often results in worsening of asthma. Therefore, avoidance of exposure to HDM allergens is often proposed. Unfortunately, the most effective and feasible avoidance strategy is still not completely assessed. Consequently, we investigated the effects of a combined HDM avoidance strategy on HDM allergen concentrations and clinical condition of allergic, mild asthmatic, patients using no inhaled steroids.

METHODS

Asthmatic patients, allergic to HDM, using no inhaled corticosteroids, were randomly allocated to an active (n = 76) or a placebo allergen-avoidance group (n = 81). Avoidance measures consisted of applying Acarosan(R) (placebo: water) to the living room and bedroom floors, and the use of HDM-impermeable covers for mattresses and bedding (placebo: cotton covers for mattresses only). Effects on allergen concentrations (Der p 1), FEV1, bronchial hyperresponsiveness, peak flow parameters and asthma symptom scores were studied during 20 weeks and controlled for the allergic status of the patients.

RESULTS

The active covers reduced Der p 1 concentrations to 9.4% (P = 0.0001), and were always significant lower than in the placebo group (P = 0.0002). Acarosan(R) resulted in slight but significant decreases (twofold, P = 0.0001), both on living room and bedroom floors, but concentrations were never significantly lower than the placebo group. Although the combined avoidance strategy resulted in a considerable reduction in allergen load in the active group, no differences were seen between the two groups in any of the clinical parameters during the follow-up period in this group of allergic asthmatics, using no inhaled corticosteroids. Corrections for the allergic status did not alter these results.

CONCLUSIONS

The combined avoidance strategy was effective in reducing HDM allergen concentration. This was especially achieved by the allergen-impermeable covers, while the effects of Acarosan(R) were only marginal. However, this allergen reduction was not reflected in a convincing improvement in clinical condition in this group of mild allergic asthmatics, using no inhaled steroids. Perhaps, a longer follow-up period would have resulted in more pronounced effects.

Do mite avoidance measures affect mite and cat airborne allergens?

BACKGROUND

Effective mite allergen avoidance measures are presumed to reduce airborne allergens yet the quantity in the air is rarely measured.

OBJECTIVE

To monitor airborne allergen during a placebo-controlled mite allergen avoidance study.

METHODS

Bedrooms of 56 atopic asthmatic children were randomly allocated to hot washing and encasing covers + acaricide (active regime) or placebo treatment. Dust was collected from the mattress, bedding and carpets; airborne allergen was measured using Casella samplers and dust settling in open Petri dishes. Der p 1, Der p 2 and Fel d 1 were measured.

RESULTS

After 24 weeks of mite allergen avoidance the Casella air-samplers collected Der p 1 less frequently in active than placebo-treated bedrooms (0 vs. 29%, P<0.05) and Petri dishes in the active group collected less than baseline (0.2 vs. 0.6 ng/day P<0.05). Homes without cats had less cat allergen than cat-owning homes and when actively treated for 24 weeks showed a greater reduction (P = 0.03) in mattress cat allergen than the placebo group.

CONCLUSION

Encasing covers and hot washing of bed linen reduced mite aeroallergen (and mattress cat allergen in the absence of cats). This could mean dual benefits to a patient sensitive to both mite and cat.

Effects of damp and mould in the home on respiratory health: a review of the literature

This review examines whether there is a direct or indirect relation between damp or mould in the home and respiratory health. Home dampness is thought to have health consequences because it has the potential to increase the proliferation of house-dust mites and moulds, both of which are allergenic. The results from the many studies conducted to investigate whether damp and mould are associated with health outcomes are difficult to compare because the methods of measuring exposures and health outcomes have not been standardized. However, the studies that have been conducted in children are probably the most reliable because the confounding effects of active smoking or occupational exposures are absent, and because the presence of symptoms of cough and wheeze have been consistently investigated in many studies. The increased risk of children having these symptoms if the home has damp or mould is fairly small with an odds ratio that is generally in the range 1.5-3.5, these estimates being statistically significant when the sample size has been large enough. This range is consistent with the measured effects of other environmental exposures which are considered important to health, such as environmental tobacco smoke or outdoor air pollutants. The potential benefits of reducing mould in the home have not been investigated, and the few studies that have investigated health improvements as a result of increasing ventilation or reducing damp in order to reduce house-dust mite levels suggest that this intervention is expensive, requires a large commitment, and is unlikely to be successful in the long term. This implies that houses need to be specifically designed for primary prevention of respiratory problems associated with indoor allergen proliferation rather than using post hoc procedures to improve indoor climate and reduce allergen load as a secondary or tertiary preventive strategy.

Allergen-avoidance measures in homes of house-dust-mite-allergic asthmatic patients: effects of acaricides and mattress encasings

This double-blind, placebo-controlled study investigated whether the application of an acaricide (Acarosan) on mattresses and on textile floor coverings in living rooms and bedrooms can contribute to improvement in lung function and airway hyperresponsiveness in 40 adult asthmatic patients sensitized to house-dust mite. In a second group of 19 patients who refused chemical intervention, the clinical effects of application of allergen-impermeable mattress encasings were studied. In all three treatment groups, Der p 1 levels in mattress dust were statistically significantly decreased after 12 months. However, this decrease was much greater in the group who received mattress encasings (final mean level 430 ng/g) than in groups with acaricide- or placebo-treated mattresses (final mean levels 1730 and 2100 ng/g, respectively). Treatment of textile floors with either Acarosan or placebo chemical caused a statistically significant decrease in the level of the house-dust-mite allergen Der p1 in floor dust. In the group with mattress encasings, no significant changes of floor dust Der p 1 were found. Airway hyperresponsiveness (as measured by the PC20 histamine) improved significantly in the mattress cover group after 6 months. The Acarosan group also showed a small but statistically significant improvement after 12 months.

Domestic mites from an acarologic perspective

Knowledge of the taxonomic, physiologic, biologic, and ecologic characteristics of allergenic domestic mites contributes to the understanding of the causation of many cases of allergic asthma, and to the measures to be taken to control excessive mite occurrence in homes. Domestic mites, i.e., the combined group of storage mites living in the home environment and of pyroglyphid house-dust mites, belong to the subclass of the acari. This comprises also many other mites of medical and economic importance, together with thousands of free-living mites. Because of some species-specific properties of their allergenic products, it is important that the producing mite is always correctly identified. In spite of their small size (approx. 0.5 mm), domestic mites have well-developed and elaborate systems of respiration, digestion, and water balance, enabling them to live and survive in the various habitats of the home environment. Knowledge of the effects of the various and changing ecologic conditions in the home environment is helpful in developing strategies to prevent the establishment and growth of large populations of allergenic domestic mites.