Allergen avoidance in house dust mite sensitive adult asthma.

Fifty adult asthmatic patients with strongly positive skinprick tests to the house dust mite were admitted into a prospective randomised controlled trial of house dust mite avoidance in the community. Twenty-two of the experimental group completed one year of dust avoidance and 19 of these tolerated the use of plastic mattress and pillow covers. Twenty of the control group (who did not alter their housecleaning habits) also completed one year of study. A fall in mite and dust levels was noted in the homes of the experimental but not the control group. Fifteen of the experimental group who completed the study were strongly RAST positive (score 3 or more) to the house dust mite. These patients had a significant improvement in FEV1/FVC, PEFR, PC20, use of treatment, and symptom score at one year, whilst the seven experimental patients who were not strongly RAST positive (score 2 or less) did not, suggesting that the change noted in the former patients was not merely due to a placebo effect. Fifteen of the control group who completed the study were also strongly RAST positive for the house dust mite and these patients showed no change in any of the parameters. This study demonstrates that adult asthmatic patients can successfully carry out house dust eradication procedures in the community over a long period of time, and that those patients who are allergic to the house dust mite appear to have both subjective and objective improvement in their asthma.