Skin diseases favouring the neck – 10 cases

Drug-induced photosensitivity dermatitis due to phenothiazine

Sharp cut-off at the border of clothing, and relative sparing of shadowed sites behind ears and under the chin, is due to light exposure. The classification of photodermatitis includes phototoxic contact dermatitis (irritant), photoallergic contact dermatitis, and drug-induced phototoxic and photoallergic dermatitis. A photodermatitis that is uniform across a skin region is likely to be due to a drug. Many medications may cause eczematous photosensitivity reactions, including thiazides, nonsteroidal antiinflammatories, antibiotics, and phenothiazines (as illustrated). The responsible drug has usually been started in the previous three weeks.

The causative medicine should be discontinued, and the rash may be treated with topical steroids and emollients.