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Author: Vanessa Ngan, Staff Writer, 2006.
A toxic or allergic reaction may occur when certain chemicals are applied to the skin and subsequently exposed to the sun. This is called photocontact dermatitis.
Photocontact dermatitis most often arises from interaction between UV radiation and one or more of the products listed below:
These products contain drugs or chemicals that are photosensitising agents (see drug-induced photosensitivity).
The reaction can be phototoxic and/or photoallergic.
Another cause of photocontact dermatitis is from the interaction of UV radiation and photosensitising compounds found in various plants. This type of dermatitis is called phytophotodermatitis. The most common plant family to cause phytophotodermatitis is the Umbellliferae family. Other plant families that cause phytophotodermatitis are Rutaceae, Moraceae and Leguninosa. The main photosensitising substances found in these plants are called furocoumarins and consist of psoralens and 5-methoxypsoralens, 8-methoxypsoralens, angelicin, bergaptol and xanthotal.
|Plant family||Plant/vegetable/fruit with furocoumarins|
The clinical features of photocontact dermatitis vary according to the photosensitising agent involved and the type of reaction it causes in the skin.
Phytophotodermatitis is a result of a phototoxic reaction and has characteristic clinical features. These include:
The main goal of treatment is to identify the photosensitising agent and if possible to avoid touching it. Photodermatitis is a self-limited problem that resolves spontaneously once the offending agent is removed or avoided.
If allergic to a sunscreen agent, choose one without the responsible chemical or select a low irritant formula that relies on metal oxides such as zinc oxide or titanium dioxide.
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