Localized hives are not caused by drugs, infections, or swallowed foods. Hives are not contagious. Most children who develop hives have them only once. The hives come and go for 3 or 4 days and then mysteriously disappear. Large swellings are common around the eyes, lips, and genitals if hives occur there.
Some young children become sensitized to mosquito or flea bites.
These hives may last for months. The best drug for hives is an antihistamine. An antihistamine won't cure the hives, but it will reduce their number and relieve itching. Benadryl, one of the most commonly used drugs for hives, has recently become available without a prescription. The main side effect of this drug is drowsiness.