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Urticaria (Hives)

December 01, 2001

By Mark B. Levin, M.D. The Pediatric Group, P.A., Princeton

 

This is the thirtyfourth article in a series written for Princeton Online.

Pink or red welts on the skin characterize urticaria, the medical terminology for hives. The welts may be as small as a mosquito bite (often-termed papular urticaria) or an inch or more in diameter. The can be sparse or so plentiful that they merge into large collections of irregularly shaped welts, called erythema multiforme. (A similar rash, called erythema marginatum, can be a consequence of an untreated by strep throat and has a flat or slightly irregular raised edge and a large skin-colored center.) Whether they are small and sparse or large and grotesque, parents are often concerned about hives.

Urticaria is a physiologic response to some event that incites an immune response. It may occur in people who are exposed to allergens (proteins that a person is allergic to). Allergens can be in foods, airborne inhalants, contact proteins applied to the skin or contained in germs (bacteria and viruses). When our bodies recognize allergens, we make specific antibodies directed against each allergen. The combination of antibodies and allergens circulate in our bloodstream until they are eliminated. While in our circulation, they cause local dilatation of the cutaneous blood vessels that allows more local blood accumulation, appearing as flat or raised red blotches in the skin. The increased blood flow to the area stimulates the cutaneous nerves, causing itching.

Since urticaria is not a disease, but rather a sign of some immune process, the treatment is directed at controlling the symptoms and eliminating the underlying trigger. Increased heat to the skin will augment the blood flow, exacerbating the hives. So, we suggest keeping an afflicted person lightly dressed. Cool bathing also helps alleviate the itching. Oral anti-itch antihistamines, such as diphenhydramine (Benadryl®), loratadine (Claritin®), hydroxyzine (Atarax®) or cetrizine (Zyrtec®), are also effective in relieving the itching, but do not cure the underlying condition. Less commonly, when urticaria is severe, oral cortico-steroids are used to alleviate symptoms.

Searching for the cause can be an exercise in frustration. The character of the urticaria is not particularly suggestive of the cause. Notable exceptions to this generality are flea bites (which usually cause papular urticaria), rhus dermatitis (poison oak, ivy and sumac which cause itchy skin lesions in a "scratch distribution" and are often mistaken for urticaria), erythema multiforme (which is most often a reaction to a viral infection or medication) and erythema marginatum (a consequence of streptococcal infection). Of course, if the trigger can be identified, avoidance is the treatment of choice. Most often, urticaria is self-limited and disappears as mysteriously as it started. If urticaria recurs or becomes chronic, keeping a calendar of foods, environmental exposures and seasonality may help pinpoint the cause. Laboratory studies and evaluation by an allergist may shed some light on the cause, but are most valuable in ruling out esoteric causes of chronic urticaria. In this situation, it is best to discuss these options with your child's physician. The appearance of urticaria does not necessarily predict a more severe allergic reaction on re-exposure to the trigger, but this is another issue that should be discussed with your child's doctor.

 

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Dr. Mark B. Levin 

Dr. Levin was a member of the staff at The Pediatric Group starting in 1977. He was an attending Pediatrician at the Medical Center at Princeton, Chairman, Department of Pediatrics, Medical Center at Princeton, 1984 to 1986, 1989 to 1992, and past President, Medical and Dental Staff, Medical Center at Princeton, 1987 to 1988. Dr. Levin served on numerous Departmental and hospital committees. He published original articles both while at Upstate Medical Center in Syracuse and at The Pediatric Group.

Moderated by Helen Rose.

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