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A. Hives are itchy red, pink, or white swellings that last a few hours before fading away, though new hives appear as old ones fade. They can be tiny or pea-sized and may join to cover broad areas of the body. While the itch can be intense, the skin is usually not scabbed or broken. A rash with fluid-filled blisters is not hives. Hives is also called "nettlerash" even when nettles are not the cause. The medical name for hives, urticaria, comes from the Latin word "urtica," meaning stinging nettle. If the condition continues for more than six weeks, it is considered chronic and is often very difficult to treat.

Cholinergic urticaria is so named because it can be produced by injections of acetylcholine, a neurotransmitter, though it is not clear that acetylcholine is the trigger for the rash. It can be induced by emotional stress, heat, or exercise. Check for other signs of cholinergic stimulation, including watery eyes, excessive salivation, and diarrhea.

Hives is usually considered an allergic reaction and treated with antihistamines such as Zyrtec or Claritin, but the allergenic trigger, if there is one, is often unknown. Sometimes hives is triggered by heat, cold, anger, pressure, light, or exercise. It is important that your daughter's physician rule out serious medical conditions such as hyperthyroidism, systemic lupus erythematosus, diabetes mellitus, and chronic renal insufficiency as possible complications.

Even though heat and exercise trigger hives, check your daughter for cold sensitivity. Wrap an ice cube in a thin plastic bag and apply to the forearm for one minute. When you remove the ice cube there will be a pale patch of skin where the ice was. If you see slight but very definite swelling over the next three-to-five minutes, as the skin warms up again, this is a positive result. If the one-minute test is negative, try three minutes and five minutes in case your daughter is only slightly sensitive to cold and should avoid it.

Since your daughter's hives started after a viral infection, her physician should also test for celiac disease, or gluten intolerance. Celiac disease is known to be associated with viral or bacterial infection, as reported in Human Immunology (June 2006, pp. 460-468). Chronic hives has been seen in patients with celiac disease, and avoiding gluten grains might reduce the hives. The symptoms of celiac disease usually include chronic diarrhea, weight loss, abdominal bloating, and anorexia. Two new "in office" blood tests for celiac disease are now available and have been proven to be quite accurate.

Compared with controls, patients with chronic hives are low in vitamins B-12, C, and E, perhaps due to an increased need for antioxidants from the production of the inflammatory substances responsible for the hives. These nutrients can be added as supplements, but combining antioxidants (vitamins A, C, and E plus selenium and bioflavonoids) both improves outcome and increases safety.