Photodermatoses: diagnosis and treatment.

BACKGROUND Sunlight induces a wide variety of dermatoses. Their differential diagnosis is problematic not only because of similar phenotypes, but also because of confusing nomenclature and classification. METHODS We selectively reviewed the literature of the past 20 years and describe the modern nosology of photodermatoses and their clinical features, diagnosis, and treatment. Readers should be able to provide correct and efficient diagnostic evaluation and treatment of patients with dermatoses induced by ultraviolet radiation. RESULTS Photodermatoses are caused by an abnormal reaction to sunlight, usually to its ultraviolet component. They are divided into phototoxic and photoallergic reactions to known photosensitizers and idiopathic photodermatoses, in which the photosensitizer is unknown. Some types are extremely rare, such as hydroa vacciniforme (prevalence 0.34 per 100,000), while others are very common, such as polymorphic light eruption (prevalence 10% to 20%). CONCLUSION Photodermatoses are not life-threatening but can cause considerable suffering. Prevention is just as important as treatment.