Photoallergic contact dermatitis to topical ketoconazole.

The differential diagnosis of photodistributed eruptions includes, among others, photoaggravated dermatoses and both systemic and contact photosensitive drug reactions, which might be of photoallergic or phototoxic nature. Consequently, dermatological evaluation must include identification of prior dermatoses and use of potentially photosensitizing systemic or topical medications. In clinical practice, it is not uncommon to encounter cases in which several of these factors concur, hence requiring investigations to elucidate the cause behind the eruption.