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11.15 Urticaria (Hives)


Presentation

The patient is generally very uncomfortable, with intense itching. There may be a history of similar episodes and perhaps a known precipitating agent (bee sting, food, or drug). Most commonly the patient will only have a rash. Sometimes this is accompanied by edematous swelling of the lips, face and/or hands (angioedema). In the more severe cases, patients may have wheezing, laryngeal edema and/or frank cardiovascular collapse (anaphylaxis). The urticarial rash consists of sharply defined, slightly raised wheals surrounded by erythema and tending to be circular or serpiginous. Each eruption is transient, lasting no more than 8-12 hours, but it may be replaced by new lesions in different locations.

What to do:

What not to do:

Discussion

Although the treatment of anaphylactic shock is beyond the scope of this book, when hypotension is present, aggressive intravenous fluid therapy should be instituted, along with the intravenous administration of the medications above. Simple urticaria affects approximately 20% of the population at some time. This local reaction is due at least in part to the release of histamines and other vasoactive peptides from mast cells following an IgE mediated antigen- antibody reaction. This results in vasodilatation and increased vascular permeability, with the leaking of protein and fluid into extravascular spaces. The heavier concentration of mast cells within the lips, face, and hands explains why these areas are more commonly affected. In asthma, the bronchial tree is more affected, whereas with eczema, the skin in knee and elbow creases is most heavily invested with mast cells and the first to develop hives.

References:


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from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
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Craig Feied, MD
Mark Smith, MD
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