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An image of a patch of sun poisoning on the left forearm
Photodermatitis, sometimes referred to as sun poisoning or photoallergy, is a form of allergic contact 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.
Signs and symptoms
Photodermatitis may result in swelling, a burning sensation, a red itchy rash sometimes resembling small blisters, and peeling of the skin. Nausea may also occur. There may also be blotches where the itching may persist for long periods of time. In these areas an unsightly orange to brown tint may form, usually near or on the face.
Many medications and conditions can cause sun sensitivity, including:
- Sulfa used in some drugs, among them some antibiotics, diuretics, COX-2 inhibitors, and diabetes drugs.
- Psoralens, coal tars, photo-active dyes (eosin, acridine orange)
- Musk ambrette, methylcoumarin, lemon oil (may be present in fragrances)
- PABA (found in sunscreens)
- Oxybenzone (UVA and UVB chemical blocker also in sunscreens) 
- Salicylanilide (found in industrial cleaners)
- St John's Wort, used to treat clinical depression
- Hexachlorophene (found in some ℞ antibacterial soaps)
- Contact with sap from Giant Hogweed. Common Rue (Ruta graveolins) is another phototoxic plant commonly found in gardens
- Tetracycline antibiotics (e.g., tetracycline, doxycycline, minocycline)
- Benzoyl peroxide
- Retinoids (e.g., isotretinoin)
- NSAIDs (e.g., ibuprofen, naproxen sodium)
- Fluoroquinolone antibiotic: Sparfloxacin in 2% of cases
- Amiodarone, used to treat atrial fibrillation
Photodermatitis can also be caused by plants. This is called phytophotodermatitis.
Prevention includes avoiding exposure to the sun and wearing sun block on the affected area.
- Cover up: wear long sleeves, slacks, and a wide-brimmed hat whenever harsh exposure is probable
- Avoid chemicals that may trigger a reaction
- Wear sunscreen at least factor 30 with a high UVA protection level
- Wear gloves and/or remain indoors after handling fruits or plants which increase sensitivity to light
- Rodriguez E, Valbuena MC, Rey M, Porras de Quintana L. 2006. Causal agents of photoallergic contact dermatitis diagnosed in the national institute of dermatology of Colombia. Photodermatol Photoimmunol Photomed 22(4): 189-192.
- Archived AAD - The Sun and Your Skin, "Allergic Reactions" section
- AAD - Sunscreens