Allergic and irritant patch test reactions and atopic disease.

This study presents a profile of patients with chronic recalcitrant eczematous disease referred by dermatologists for contact allergy evaluation. Allergic contact dermatitis (ACD) and irritant responses were carefully defined, as was the presence or absence of atopy obtained by history. Of 410 patients studied, 44% had no history of atopic disease and 46% were classed as definitely atopic. Among relevant ACD patch test reactors (n = 198), 51.5% had atopy, compared with 40.9% with no atopy but this difference was not significant. Likewise, among atopics (n = 189), 54% had definite, relevant ACD patch test responses while 33.9% had negative ACD (again not significant). Significance was seen in the higher mean number of positive allergic patch tests in the atopic group (2.7 versus 2.0, p = 0.0223). Irritant patch tests were highest among patients with both ACD and atopy (p = 0.0308) and the proportion of irritant responses correlated with increasing numbers of positive ACD tests. We conclude that atopics are at least as likely to have ACD as are non-atopics. Irritancy is increased in these patients with chronic dermatitis and the frequency of irritant reactions correlates with both greater numbers of ACD responses and with presence of atopy.

The spectrum of cutaneous patch-test reactions in patients with atopic dermatitis.

We have outlined rationale and problems associated with three types of patch tests that may provide diagnostic help in patients with difficult-to-manage AD. Each of these methods is imperfect and in need of greater study using a critical approach, better techniques, more attention to irritant controls, and better definition of atopic populations. Proof of validity for aeroallergen patch testing will necessarily require large quantities of purified antigens. In spite of all these problems, patch testing can be useful and sometimes essential for the diagnosis and management of difficult AD.