Phototoxicity

Phototoxicity is a chemically induced skin irritation, requiring light, that does not involve the immune system. It is a type of photosensitivity. The skin response resembles an exaggerated sunburn. The involved chemical may enter into the skin by topical administration or it may reach the skin via systemic circulation following ingestion or parenteral administration. The chemical needs to be "photoactivated" by light in the UVA spectrum. The mechanism of action varies — the chemical may become excited by light and directly damage surrounding tissue, or it may lead to the formation of free radicals that damage tissue indirectly.

Causes

Phototoxicity can be caused by various agents:

• Certain medications, such as tetracycline, sulphonamides, quinolones, phenothiazines, and psoralens
• Certain essential oils, such as bergamot, lime, lemon, grapefruit, cedar, and fig
• Certain plants, such as giant hogweed, wild parsnip, lemon verbena, and St John's wort
• Certain chemicals, such as furocoumarins, coumarins, and xanthotoxin

Symptoms

Symptoms of phototoxicity can include:

• Redness (similar to sunburn)
• Swelling
• Itching
• Burning
• Blisters and scaling
• Hyperpigmentation (dark patches on the skin)

Treatment

Treatment for phototoxicity is similar to the treatment for a severe sunburn. This can include:

• Cold compresses
• Over-the-counter hydrocortisone creams
• Non-prescription pain relievers
• Stay out of the sun as much as possible until the skin has healed

Prevention

Prevention of phototoxicity involves avoiding known triggers, such as certain medications, plants, and chemicals. If exposure cannot be avoided, protective clothing and sunscreens may help prevent a reaction.

See also

• Phototoxicity (eye)
• Photoallergy
• Photosensitivity in humans
• Drug-induced photosensitivity
• Photodermatitis

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