CAUSES OF URTICARIA
(Most important factors, but not necessarily the most common, are indicated by bold letters.)

Drugs And Chemicals

Salicylates, Indomethacin and other nonsteroidal anti-inflammatory drugs, Opiates, Radiocontrast media, Penicillins, Sulfonamides, Sodium benzoate Insulin, Micenthol (cigarettes, toothpaste, iced tea, hand cream, lozenges, candy), Tartrazine - a dye (vitamins, birth control pills, antibiotics, TDC yellow #5)

CONTACTANTS

Latex, perfumes, wool


FOODS
Tree nuts (walnuts, e.g.), peanuts, fish, crustaceans, bananas, soybeans, tomatoes, eggs, milk, berries, wheat

PHYSICAL STIMULI
Simple friction or scratching (dermatographism), sunlight, pressure, heat, cold temperature, water, vibration

INHALANTS
Latex, dust mite, animal danders, pollen

INFECTIONS
Viral upper respiratory infections, bacterial (sinusitis, dental abscess, otitis),viral hepatitis, vaginitis, fungal (tinea pedis - athelete's foot), helminth, protozoa

SYSTEMIC DISEASES
Collagen vascular diseases, leukemia, lymphoma, endocrinopathies (Hyper- and hypothroidism, Hashimoto's thyroiditis), menstruation


TREATMENT
Eliminating the etiologic agent is the best way to treat chronic urticaria. When the cause of chronic urticaria cannot be found, drug therapy enables most patients to live normal lives. It is important to emphasize that patients should take the prescribed dose and not use the medication on an "as-needed" basis.

In the great majority of cases, the lesions of chronic urticaria can be controlled with oral antihistamines. A "non-sedating" antihistamines (loratidine, fexofenadine, e.g.) should be the first choice since they have minimal side effects. Although sedating in a slightly higher percentage of patients than the previous drugs, cetirizine (a metabolite of hydroxyzine) is also very effective in chronic urticaria. Although some clinicians feel that cetirizine is the most effective of the "non-sedating" antihistamines for urticaria, there are no good clinical trials directly comparing these drugs.

When these drugs fail, a trial of "classical" antihistamines is warranted. Hydroxyzine, although often sedating, can be used in a single nighttime dose. This drug can be quite effective if high enough doses are given. For those with resistant hives, a morning dose of a less sedating antihistamine can be added to the regimen. The most potent antihistamine, however, is probably the anti-depressant doxepin. Although adverse effects (including sedation, increased appetite, and possible cardiac effects) often limit its use, doxepin is perhaps the most effective of all the antihistamines for urticaria and angioedema (often 10 to 25 mg at bedtime can be quite effective).

Tolerance to the sedative effects of these antihistamines usually occurs within several days of therapy, with no significant drop off in the beneficial effects. However, decreased hand-eye coordination, for example, can occur in the absence of drowsiness.

In theory, adding an H2-blocker (e.g., cimetidine, ranitidine) to the regimen should be helpful since these drugs block histamine receptors - again, there is little data to support this practice. Our results with adding H2-blockers have been quite variable. There have also been reports of benefit with beta-adrenergic drugs (terbutaline, e.g.) and calcium-channel blockers,
but again, they are limited numbers of trials to support the use of these drugs. Whatever the case, a discussion of risks and benefits should take place.

Unfortunately, however, a few patients respond only to systemic steroids. In this case the best mode of action is to give a short burst with a moderate dosage (e.g., prednisolone 1 mg/kg/day), and then try to taper the dose of steroid as antihistamines are introduced.

REFERENCES
Tharp M. Chronic Urticaria: Pathophysiology and treatment approaches. J Allergy Clin Immunol 1996;98:S325-30.

Volonakis M. et al. Etiologic factors in childhood chronic urticaria. Ann Allergy 1992;69:61-5.

Greaves, M. Current Concepts: Chronic Urticaria. NEJM 1995;332:1767-71.

Neil Gershman, MD Chronic Urticaria Summary 4