Photodermatitis

Adverse reactions to the sun's rays have become more commonplace because an increasing number of photosensitizers are entering our environment from industrial, cosmetic, and pharmaceutical sources. Two types of photosensi-tivity can occur: phototoxic and photoallergic. Clinically, these reactions usually resemble sunburn (31-33).

Phototoxic reactions may be induced by endogenous or exogenous chemicals. Endogenous photosensitizers made by the body include porphyrin molecules. Exogenous photosensitizers may arrive on the skin through topical applications or may be distributed through the body by the blood flow. Topical photosensitizers are found in cosmetics, medications, plant, and industrial and air pollutant emissions. Plant sensitizers include celery, carrots, grasses, and lime. Systemic photosensitizers are primarily medications (31-33).

Acute and chronic phototoxic reactions may occur. The acute response is characterized by erythema and edema followed by hyperpigmentation and desquamation. The end point of chronic damage may be cutaneous cancer formation as a result of nucleic acid and cytoplasmic molecular injury. Treatment consists of removal of the offending agent and systemic steroids (31-33).

Photoallergy is uncommon and acquired through altered reactivity to an antigen. The immune response may be antigenic or cell mediated and presents with urticaria or eczema. Examples of substances causing photoallergic reactions include musk ambrette (after-shave), hydroxychloroquine, ketopro-fen, and celecoxib. Treatment is removal of the offending substance and systemic steroids (31-33).

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