Hives

 Dermographism is a form of hives that develops when the skin is rubbed, stroked, or pressured. Hives usually appear shortly after exposure to an allergen and can show up anywhere on the skin. They may be harmless and disappear within hours, or they may be an early symptom of anaphylaxis.
Some Likely Triggers For Hives Are:
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Foods mainly berries, seafood, nuts, tomatoes, eggs, and wheat
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Food additives, especially dyes and preservatives.
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Drugs or medication, including aspirin and penicillin
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Insect bites or stings.
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Any number of substances including fabrics and detergents (although hives from contact reactions are rare).
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Physical stimuli such as a cold swimming pool or a hot shower, sudden temperature changes, sunlight, exercise, vigorous toweling after bathing, or tight clothing.
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Cold weather. (If you suspect a cold allergy and want to test yourself, wrap an ice cube in plastic and hold it to your skin for 30-60 seconds. A raised welt indicates a positive reaction.)
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Chemical fumes.
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Stress and anxiety
Treat hives with oral antihistamines around the clock, anti itch lotion, if necessary, and avoid all suspected allergens. If the welts don't vanish in 48 hours, see your doctor.