1. Patients and controls: Samples of dust from homes were taken during the run-in period before patients with AD embarked on a controlled clinical trial of house dust mite eradication. Twenty-three adult patients (11 males, 12 females; age range 16~56 years) with symptomatic AD were rеcruited at the out-patient clinic or the Department of Dermatology, Western Infirmary, Glasgow. They all showed positive immediate skin prick-tests to Dermatophagoides pteronyssinus extract, and positive anti-D. pteronyssinus RAST scores, as well as elevated total serum IgE. Twenty-three healthy nonatopics were selected from nominees of the author's acquaintances. They had no personal or family history of atopy or exfoliative skin disease. The sex ratio and age range of the group were similar to the group with atopic dermatitis (10 males, 13 females; age range 19~51 years). All members of both groups dwelt within Greater Glasgow, U. K., and none had previously conducted mite eradication procedures in their homes.

2. Dust sampling and mite extraction techniques: Single dust samples were taken from the mattress of each person between January and March, 1985, as follows: dust was collected from the surface of each mattress into a plastic sampling tube with a 10-um mesh dust-trap, attached to a portable vacuum pump. The area from which dust was collected was standardized to 0.25 m² by using a zig-ziag sampling pattern of 20 X 1 m long sweeps, taken in 1 min, with a sampling nozzle with an internal diameter of 12.5 mm.