Photodermatitis

Photodermatitis, sometimes referred to as sun poisoning or photoallergy, is a form of allergic dermatitis in which the allergen must be activated by light to sensitize the allergic response, and to cause a rash or other systemic effects on subsequent exposure. The second and subsequent exposures produce photoallergic skin conditions which are often eczematous. It is distinct from sunburn.

Some variants are caused by topical exposure, while others are caused by medications, and still others are caused by medical conditions which generate the allergen precursors in the body.