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.