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 wor sening of asthma. Therefore, avoidance of exposure to HDM allergens is ofte n proposed. Unfortunately, the most effective and feasible avoidance strate gy is still not completely assessed. Consequently, we investigated the effe cts 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 corticosteroi ds, were randomly allocated to an active (n = 76) or a placebo allergen-avo idance 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, bronc hial hyperresponsiveness, peak how parameters and asthma symptom scores wer e studied during 20 weeks and controlled for the allergic status of the pat ients. Results The active covers reduced Der p 1 concentrations to 9.4% (P = 0.000 1), 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 nev er significantly lower than the placebo group. Although the combined avoida nce strategy resulted in a considerable reduction in allergen load in the a ctive 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 a sthmatics, using no inhaled corticosteroids. Corrections for the allergic s tatus did not alter these results. Conclusions The combined avoidance strategy was effective in reducing HDM a llergen concentration. This was especially achieved by the allergen-imperme able covers, while the effects of Acarosan(R) were only marginal. However, this allergen reduction was not reflected in a convincing improvement in cl inical condition in this group Of mild allergic asthmatics, using no inhale d steroids. Perhaps, a longer follow-up period would have resulted in more pronounced effects.