Atopy and Contact Allergy

Abstract

Impairment of cellular immunity is one of the characteristic immunological features found in patients with atopic eczema. For example, in vitro there are decreased lymphocyte responses to stimulation with mitogens and antigens. In vivo sensitization studies with neoantigens (e. g., dinitrochlorobenzene) have disclosed a clearly reduced reactivity in patients with atopic eczema compared to controls. This leads to the assumption that there may be a reduced frequency of allergic contact sensitization in patients with atopic eczema. However, the pertinent literature on the prevalence of allergic contact sensitization in patients with atopic eczema does not allow one to draw definite conclusions. The results are contradictory, reporting lower, equal, and higher sensitization rates in atopic eczema. Interpretation is hampered by methodological flaws, as most of the studies are retrospective and often without adequate controls. When comparing patients with atopy to nonatopic individuals, we did not find a difference with regard to the overall reactivity rate to compounds of the patch test standard series; however, there were differences when the frequency of reactions to individual compounds was considered. Thus, there was a significantly higher frequency of contact sensitization to nickel sulphate (15.2%/10.0%), potassium dichromate (5.9%/4.3%), and thiu-ram mix (4.2%/2.6%) in atopics than in nonatopics. In contrast, contact allergy to balsam of Peru (5.3%/6.7%), wool alcohols (2.9%/4.3%), neomycin (2.4%/ 3.5%), and parabens (0.8%/2.1%) was significantly less frequent in atopics than in nonatopics. However, as atopics were younger than nonatopics, these findings may be explained at least in part by the age difference. Current knowledge suggests that atopy does not protect against allergic contact sensitization. Further studies are necessary to clarify the relationship between contact allergy and atopy.