Eyelid dermatitis: contact allergy to 3-(dimethylamino)propylamine.

We present the case of a 42-year-old woman with intractable eyelid dermatitis. Patch testing revealed sensitization to 3-(dimethylamino)propylamine (DMAPA). DMAPA is an important etiology of allergic contact dermatitis of the eyelids and face but is easily missed even with expanded-series patch testing. We also review the most common causative allergens in eyelid dermatitis cited in the literature over the past decade. DMAPA is a reagent used in the formation of cocamidopropyl betaine (CAPB), a common additive to liquid soaps, shampoos, and other cleansing products because of its utility as a surfactant. Beginning in the 1980s, reports of allergy to CAPB surfaced in the literature. Ultimately, a majority of patch testing studies have shown that clinical allergy to CAPB-containing products actually reflects allergy to contaminant DMAPA in most cases. Amidoamine, another intermediate in the formation of CAPB, may also be implicated through a proposed mechanism of conversion to DMAPA in the skin. When patch-testing for eyelid and facial dermatitis, it is crucial to test with DMAPA directly, not just with CAPB; unlike commercial-grade CAPB, the CAPB in patch test kits is ultrapure and does not contain contaminant DMAPA.