Contact dermatitis as a systemic disease.

Systemic contact dermatitis (SCD) is a condition occurring in previously sensitized individuals after systemic re-exposure to the same or cross-reacting substance. Systemic route of administration means uptake of an allergen via percutaneous, transmucosal, oral, intravenous, intramuscular, and inhalational routes, as well as through implants. The intimate mechanisms behind SCD are not yet fully understood, but it is thought to be a T-cell mediated delayed type hypersensitivity reaction. The most common allergens recognized to date are nickel, aminoglycoside antibiotics, corticosteroids, balsam of Peru, and plants from the Anacardiacae and Compositae families. The most typical presentation of SCD, known as baboon syndrome, includes diffuse erythema of the buttocks, the upper inner surface of the thighs, and the axillary folds. Cases with the classical baboon pattern of distribution elicited by systemically introduced drugs without previous sensitization are encompassed by the acronym SDRIFE (Symmetric Drug-related Intertriginous and Flexural Exanthema). Interestingly, corticosteroids, although widely applied for anaphylaxis and other allergic conditions, can produce sensitization, and they are commonly mentioned as triggers of SCD.