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In photoallergic dermatitis, sunlight and exposure to the offending substance usually affect the face and arms, but the sun-shaded area under the chin is generally spared. Although sunlight is essential for the initiation of photosensitization, the dermatitis may continue long after the photoallergy is eliminated (a condition known as a “persistent light eruption”). 9 Common photoallergic substances include fruits and vegetables (., limes, celery, parsnips), hydrocarbons (., coal tar, pitch, asphalt, anthracene), and drugs (., tetracycline, thiazide diuretics, phenothiazines, sulfonamides) and fluorescein dye. 3