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URTICARIA AND ANGIONEUROTIC EDEMA
Urticaria (hives) is a type I hypersensitive allergic reaction of the skin characterized by the sudden appearance of pinkish, edema-tous elevations that vary in size and shape and itch and cause local discomfort. They may involve any part of the body, including the mucous membranes (especially those of the mouth), the larynx (occasionally with serious respiratory complications), and the gas-trointestinal tract.
Each hive remains for a few minutes to several hours before disappearing. For hours or days, clusters of these lesions may come, go, and return episodically. If this sequence continues for longer than 6 weeks, the condition is called chronic urticaria (Tierney et al., 2001).
Angioneurotic edema involves the deeper layers of the skin,resulting in more diffuse swelling rather than the discrete lesions characteristic of hives. On occasion, this reaction covers the en-tire back. The skin over the reaction may appear normal but often has a reddish hue. The skin does not pit on pressure, as ordinary edema does. The regions most often involved are the lips, eyelids, cheeks, hands, feet, genitalia, and tongue; the mucous mem-branes of the larynx, the bronchi, and the gastrointestinal canal may also be affected, particularly in the hereditary type (see sec-tion that follows). Swellings may appear suddenly, in a few sec-onds or minutes, or slowly, in 1 or 2 hours. In the latter case, their appearance is often preceded by itching or burning sensations. Seldom does more than a single swelling appear at one time, al-though one may develop while another is disappearing. Infre-quently, swelling recurs in the same region. Individual lesions usually last 24 to 36 hours. On rare occasions, swelling may recur with remarkable regularity at intervals of 3 to 4 weeks.
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