skin disorders
Photosensitivity Reactions
Chemical photosensitivity
Over 100 substances, swallowed or applied to the skin, are known to cause sun-induced reactions on the skin. A limited number cause most reactions (see table). There are 2 types of chemical photosensitivity: phototoxicity and photoallergy. Inphototoxicity,people have pain and develop redness, inflammation, and sometimes brown or blue-gray discoloration in areas of skin that have been exposed to sunlight for a brief period. These symptoms resemble those of sunburn, but the reaction differs from sunburn in that it occurs only after the person has swallowed certain medications (such as tetracyclines or diuretics) or chemical compounds or has applied them to the skin (such as perfume andcoal tar). Some plants (including limes, celery, and parsley) contain compounds called furocoumarins that make some people's skin more sensitive to the effects of UV light. This reaction is called phytophotodermatitis. All phototoxic reactions appear only on areas of skin that have been exposed to the sun. They usually develop within hours after sun exposure. Inphotoallergy,an allergic reaction causes redness, scaling, itching, and sometimes blisters and spots that resemble hives. This type of reaction can be caused by aftershave lotions, sunscreens, and sulfonamides. Substances that cause photoallergy are capable of doing so only after the person has been exposed to both the substance and sunlight (because sunlight is what makes the substance capable of triggering photoallergy). Photoallergic reactions can also affect areas of skin that have not been exposed to the sun. They usually develop 24 to 72 hours after sun exposure. Antianxiety medications Alprazolam Chlordiazepoxide Antibiotics Quinolones Sulfonamides Tetracyclines (especiallydoxycycline) Trimethoprim Antidepressants Tricyclic antidepressants Antifungal medications Griseofulvin Antihyperglycemics Sulfonylureas Antimalarial medications Chloroquine Quinine Antipsychotics Phenothiazines Chemotherapy medications Dacarbazine Fluorouracil Methotrexate Vinblastine Diuretics Furosemide Thiazides medications used to treat acne Isotretinoin Heart medications Amiodarone Quinidine Pain-relief medications (analgesics) Nonsteroidal anti-inflammatory drugs (NSAIDs; especiallypiroxicamandketoprofen) Sensitizing substances Antibacterials applied to the skin (such aschlorhexidineandhexachlorophene) Coal tar Fragrances Furocoumarins present in plants, such as limes, celery, and parsley Sunscreens 