Sweat-related dermatoses: old concept and new scenario.

This review focuses on dermatoses that are caused by the presence of sweat--a previously underemphasized subject. A working classification based on 'internal sweating' (extravasated sweat in the dermis and epidermis) and 'external sweating' (sweat on skin surface) is proposed. Clinical observations suggest that transient acantholytic dermatosis is the consequence of extravasated sweat; we speculate that it is an example of sweat-related, protease-induced epidermal acantholysis. Neutrophilic eccrine hidradenitis may represent a sweat-related drug reaction. We emphasize the well-recognized phenomenon of 'sweat retention syndrome' in a new scenario: hospitalized febrile patients, increasing use of chemotherapy, new life style. The concept of 'sweat-gland-mediated cutaneous inflammation' is proposed.