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[L. urtica, nettle]
An allergic reaction marked by multiple discrete swellings on the skin (wheals) that are intensely itchy and last up to 24 hr. The wheals appear primarily on the chest, back, extremities, face, or scalp.
SYN: SEE: hives
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URTICARIA ; SEE: allergy; SEE: angioedema

Urticaria is caused by vasodilation and increased permeability of capillaries of the skin due to the release by mast cells of vasoactive mediators. The mast cell degranulation is due to an immunoglobulin E-mediated reaction to allergens (such as foods, drugs, or drug additives), heat, cold, and, rarely, infections or emotions. Urticaria is a primary sign of local and systemic anaphylactic reactions. It affects people of all ages but is most common between the ages of 20 and 40. Angioedema is frequently associated with urticaria.

Drugs that block histamine-1 (H1) receptors (antihistamines) are the primary treatment for urticaria. The use of both H1 and H2 receptor blockers has been recommended but has not been proven more effective. Patients should avoid identified allergens. Doxepin, calcium channel blockers, or immunosuppresive drugs may be needed for symptoms that are not well controlled with antihistamines. Known triggers of urticaria should be avoided.

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