Hives are itchy, red welts or small bumps that last from 15 minutes to 24 hours. They usually appear suddenly and leave no trace when they disappear (unless they have been scratched). Crops of hives may appear several times a day. They may come and go for days or weeks, sometimes longer.
Hives are common, affecting 10-20% of the population at least once in their lifetime. Hives are certainly annoying, but are otherwise harmless unless they cause throat swelling; this is rare but requires immediate treatment.
What causes hives?
Hives may be caused by something taken internally, most often a medicine such as penicillin or aspirin. Sometimes foods cause hives. Shellfish, nuts, eggs, milk, strawberries and food additives are well-known examples. Hives may appear within minutes or up to several hours after eating.
Hives in children are often caused by infections such as a virus or strep throat, but are rarely the sign of more serious internal disease. Occasionally, physical agents such as pressure or cold can cause hives.
How is it treated?
In treating your or your child’s hives, we try to find a cause, but this is not always possible. It may be helpful to keep a record of foods or other ingested items (for example, vitamins, medicines and herbal supplements). However, in 90% of cases we cannot discover the underlying.
Hives are usually controlled with antihistamines, but in order for the antihistamines to prevent the hives from forming, they usually need to be given several times a day, not just when the hives are present. They also help the itching. Some antihistamines cause drowsiness and may only be tolerated at nighttime. Others are non-sedating. Occasionally, antihistamines may make a child hyperactive.
Corticosteroids may need to be prescribed to control the hives and provide symptomatic relief. Hives usually improve within days after medication is begun.