11.15 Urticaria (Hives)
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agk's Library of Common Simple Emergencies

Presentation
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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:
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- Attempt to elicit a precipitating cause, 
    including drugs, foods, stress, or an 
    underlying infection or illness, (e.g., 
    collagen vascular disease, malignancy, or, 
    when accompanied by arthralgias, anicteric 
    hepatitis).
- For immediate relief of severe pruritis, you 
    can try 0.3cc of epinephrine (1:1000) 
    subcutaneously, but this wears off quickly, 
    and adds a number of side effects the patient 
    may find worse than the itching: tachycardia, 
    shaking, dry mouth, wet palms, hypertension, 
    and even angina and myocardial infarction.
- For continued relief administer diphenhydramine 
    (Benadryl) or hydroxyzine (Vistaril) 50mg po.
- For prolonged relief from itching prescribe 
    diphenhydramine (Benadryl), hydroxyzine 
    (Atarax) 25-50mg, cyproheptadine 
    hydrochloride (Periactin) 4mg qid or 
    terfenadine (Seldane) 60mg bidfor the next 48 
    hours.
- To reduce the rash, prescribe cimetidine 
    (Tagamet) 300mg q6h. Other H2 blockers, such 
    as ranitidine (Zantac) and nizatidine (Axid) 
    also appear to work in similar doses.
- To blunt the entire allergic process, give 
    prednisone 60mg po now and prescribe 20mg qd 
    for 2 days.
- Inform the patient that the cause of hives 
    cannot be determined in the vast majority of 
    cases. Let him know that the condition is 
    usually of minor consequence but can at times 
    become chronic, and, under unusual 
    circumstances, is associated with other 
    illnesses. Therefore, the patient should be 
    provided with elective followup care.

What not to do:
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- Do not have the patient take aspirin. Some 
    patients experience a worsening of their 
    symptoms with the use of aspirin. Morphine, 
    codeine, reserpine, and alcohol, as well as 
    certain food additives such as tartrazine 
    dye, are often allergens or potentiate 
    allergic reactions, and benzoates should 
    probably also be avoided.

Discussion
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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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- Rusli M: Cimetidine treatment of recalcitrant 
    acute allergic urticaria. *Ann Emerg Med* 
    1986;15:1363-1365.

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