Information on the following diseases can be found in the Related Disorders section of this report:

• Physical urticaria
• Cholinergic urticaria

The first symptom of papular urticaria is usually itching (pruritus). This is followed shortly by the appearance of elevated ridges (wheals) that may remain small or become large. The larger wheals tend to be clear in the center, and may be noticed first as large rings of redness of the skin (erythema) and swelling (edema). Ordinarily, crops of hives come and go. A lesion may remain for several hours, then disappear only to reappear elsewhere.

Angioedema is a more diffuse swelling of loose tissue under the skin usually affecting the back of hands or feet, lips, genitalia and mucous membranes. Swelling (edema) of the upper airway may produce respiratory distress, and the high-pitched tone of difficult breathing may be mistaken for asthma.

Acute papular urticaria and angioedema are essentially exaggerated allergic reactions limited to the skin and tissues just under the skin (subcutaneous tissues). The reaction may be caused by a drug allergy, by insect stings or bites, by desensitization injections (allergy shots) or ingestion of certain foods (particularly eggs, shellfish, nuts or fruits) by people who are allergic to these substances. In some cases (such as reactions to strawberries), the reaction may occur only after overindulgence, and possibly result from direct toxic histamine release into the blood. If acute angioedema is recurrent, progressive, and never associated with urticaria, a hereditary enzyme deficiency should be suspected.

Children from 2 to 7 years are most commonly, but not exclusively, affected by papular urticaria. Children are especially susceptible in the summertime when the insect population increases. It is more rare in adults, perhaps in part because adults build up a tolerance.

Physical urticaria is a condition in which red allergic skin lesions and itching are produced by exposure to cold temperatures, water or mild trauma.

Cholinergic urticaria is a condition characterized by red spots on the skin, itching and possibly abdominal cramps, diarrhea, faintness, weakness and sweating. It is caused by sensitivity to heat, sunlight, exercise, etc. For more information on these disorders and other types of urticaria, choose "urticaria" as your search term in the Rare Disease Database.)

Acute papular urticaria is a self-limited condition that generally subsides in 1 to 7 days. Therefore, treatment is chiefly symptomatic. If the cause is not obvious, all nonessential medication should be stopped until the reaction has subsided. Symptoms such as itching and swelling can usually be relieved with a topical soothing agent such as calamine lotion or oral antihistamine. Corticosteroids (e.g. prednisone) may be necessary for the more severe reactions, particularly when associated with angioedema. Topical corticosteroids are of no value. More serious attacks may bring on airway obstruction that may require an opening in the trachea (tracheotomy).

Although the specific cause of chronic papular urticaria can seldom be identified and removed, spontaneous remissions usually occur within 2 years in about half of the cases. Control of stressful life situations often helps. Certain drugs (e.g. aspirin) may aggravate symptoms, as can alcoholic beverages, coffee and tobacco. If so, they should be avoided.

Oral antihistamines are beneficial in most cases. All reasonable measures should be used before resorting to corticosteroids, which are frequently effective but have significant side effects after chronic use. A few patients with urticaria that doesn't respond to treatment (intractable) may have a hyperthyroid condition.

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

TEXTBOOKS
Beers MH, Berkow R., ed. The Merck Manual, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999:1054-56.

Berkow R., ed. The Merck Manual-Home Edition.2nd ed. Whitehouse Station, NJ: Merck Research Laboratories; 2003:1071-72.

Bennett JC, Plum F. ed. Cecil Textbook of Medicine. 20th ed. W.B. Saunders Co., Philadelphia, PA; 1996:1420-21.

REVIEW ARTICLES
Steen CJ, Carbonaro PA, Schwartz RA. Arthropods in dermatology. J Am Acad Dermatol. 2004;819-42.

Demain JG. Papular urticaria and thins that bite in the night. Curr Allergy Asthma Rep. 2003;3:291-303.

Dunlop K, Freeman S. Caterpillar dermatitis. Australas J Dermatol. 199738:193-95.

FROM THE INTERNET
Stibich AS. Papular Urticaria. emedicine. Last Updated: June 4, 2003. 7pp.
www.emedicine.com/derm/topic911.htm