Urticaria: usually a delayed allergic reaction, could be something from weeks ago. Often a reaction to a cold virus, oddly enough.
Contrary to popular belief, most of the serious allergic reactions (rash, facial swelling, anaphylaxis etc but not contact dermatitis) is triggered by re-exposure to an allergen. It's never caused by something new. Dermatitis and eczema can be aggravated by new things however.
Urticaria is down in the less-serious part of the allergic reactions spectrum - benign, but irritating and dramatic. Anti-histamines and calamine lotion can help reduce the itch while you wait for it to go.
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Allergies are tricksy.
Date: 2008-07-17 06:24 am (UTC)Contrary to popular belief, most of the serious allergic reactions (rash, facial swelling, anaphylaxis etc but not contact dermatitis) is triggered by re-exposure to an allergen. It's never caused by something new.
Dermatitis and eczema can be aggravated by new things however.
Urticaria is down in the less-serious part of the allergic reactions spectrum - benign, but irritating and dramatic. Anti-histamines and calamine lotion can help reduce the itch while you wait for it to go.