A study of white dermographism in atopic dermatitis.

Vascular responses of 15 adults with atopic dermatitis (AD), 15 with psoriasis and 15 with normal skin were studied using an automated dermographometer we have designed. The type of colour change, time to onset and the duration of responses were recorded after a constant stroking force was applied to the skin of each subject. Of the 15 patients with atopic dermatitis, 11 had white dermographism (WD) with abnormal looking skin and four had red dermographism (RD) with normal looking skin. All the control subjects had RD. WD in AD had a significantly longer time to onset and shorter duration of response than RD in controls (P < 0.01), whereas RD in AD had a significantly shorter duration of response than RD in controls (P < 0.01). WD in AD changed to RD after topical corticosteroid treatment and this post-treatment RD was quantitatively similar to the RD in AD. We have quantified, for the first time, a subnormal form of RD in clinically normal skin of patients with AD, which is different from that of the RD in normal subjects. We have also shown that WD in AD is altered to this subnormal form of RD after treatment with topical coricosteroids.