Urticaria (hives) presents with an intensely itchy rash of raised wheals that last less than a day. It is usually caused by an allergic reaction but the precipitating agent is often unknown. Treatment involves antihistamines like diphenhydramine to relieve itching. Cimetidine can reduce the rash. For severe cases, epinephrine or corticosteroids may be needed. The condition is usually minor but can become chronic, so follow-up is recommended to monitor for underlying illnesses. Aspirin and other substances should be avoided as they may worsen symptoms. Hives are caused by the release of histamine from mast cells, causing swelling and itching.

1. 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:
• 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:
• Do not havethe 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.

2. 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.