Photosensitivity

Abnormal reaction to sunlight. Photosensitivity usually causes a rash on skin exposed to sunlight. This often occurs because a photosensitizer (such as some drugs, dyes, chemicals in perfumes and soaps, and plants such as mustard) has been ingested or applied to the skin. Photosensitivity is also a feature of disorders such as systemic lupus erythematosus. People who are susceptible to photosensitivity reactions should avoid exposure to sunlight and photosensitizers, and use sunscreens.