Ultraviolet (UV) radiation causes both acute and chronic skin changes. Sunburn is a partial-thickness burn, which may become a full-thickness injury if infected. “Sun poisoning” is a severe systemic reaction to UV radiation. Patients may complain of nausea, vomiting, headache, fever, chills, and prostration. Excessive UV radiation may cause injury to the cornea and conjunctiva, termed UV keratitis (photokeratitis, snow blindness). This painful condition may occur in skiers, welders, or tanning salon patrons who do not wear proper eye protection.
There are several types of photosensitivity reactions (photodermatoses). Phototoxic reactions are abnormal responses to UV radiation caused by substances that are ingested (eg, prescription or over-the-counter medications) or applied to the skin. There is a direct relation between the amount of UV exposure and severity. Photoallergic reactions are clinically similar to contact dermatitis and, like phototoxic reactions, may be precipitated by ingested or applied drugs. Unlike phototoxic reactions, photoallergies may be precipitated by a small amount of light. Phytophotodermatitis is precipitated by skin contact with certain plants followed by exposure to UV radiation.
Sunburn. Sunburn is characterized by erythema, edema, warmth, tenderness, and blisters. (Photo contributor: Kevin J. Knoop, MD, MS.)
Healing UV Exposure. This patient suffered significant UV exposure with resultant sunburn in the Himalayas. Darkly pigmented skin provides limited protection in high-altitude subtropical areas with very high amounts of UV exposure. Note the sparing of the periorbital areas secondary to the wearing of appropriate eye protection. (Photo contributor: Luanne Freer, MD.)
Tanning Bed Burn. This patient suffered a severe diffuse partial-thickness burn from prolonged UV exposure in a tanning bed. Note the sharp demarcation on the buttocks at the point where the patient was partially protected by his pants. (Photo contributor: R. Jason Thurman, MD.)
Phytophotodermatitis. This reaction may require aggressive systemic steroid therapy. The case illustrated is a mild one caused by exposure to limes and UVA. A clue to the diagnosis is the patchy distribution with linear edges. More severe reactions resemble rhus dermatitis. (Photo contributor: Lee Kaplan, MD.)
Phytophotodermatitis—Cow Parsnip. Severe phytophotodermatitis caused by exposure to cow parsnip (Heracleum lanatum) in Alaska. Another name for cow parsnip is “pushkie,” so this is also known locally as “pushkie burn.” (Photo contributor: Kathy McCue, MD.)
Phytophotodermatitis—Lime. Phytophotodermatitis caused by exposure to limes and UV radiation in Jamaica. The patient had been exposed while riding shirtless on a horse through a lime orchard. (Photo contributor: Stephan Russ, MD.)