A: Karrie, you're not alone—one in five children develops hives at one time or another. Hives are a skin rash of raised red welts of various sizes that can come and go over different parts of the body. Sometimes they're very itchy, and sometimes not. Usually hives go away within a couple of days, but they can last for weeks or months, as in your son's case.

Hives are generally caused by an allergic reaction to one of the following:

• Food: e.g., peanuts, tree nuts, eggs, milk, fish, shellfish, berries, and food coloring
• Medication: e.g., antibiotics such as penicillin and amoxicillin
• Bite or sting from a bee or other insect
• Pollen, plant, or animal dander or saliva

Hives can also be a response to other triggers including:

• A virus infection
• Cold, heat, pressure, or emotional stress

It would be great if you could determine the cause of your son's hives in order to prevent another reaction in the future. However, it's often impossible to determine the cause.

It's a good idea to consult your pediatrician about your son's hives. The doctor can help review your child's diet and exposure to any of the other factors to determine what might have triggered the hives. The doctor may or may not recommend trying to eliminate possible allergy-producing foods from your son's diet. As you say, it can be complicated to change his diet, but you might try eliminating some of the most likely suspects (e.g., peanut butter, eggs, fish, and shellfish) to see if it helps. The doctor might also prescribe an antihistamine medication to try to end the outbreak of hives. If the hives are itchy, you can give your son baths with baking soda, oatmeal, or chamomile tea to help relieve the itching.

Since allergies are hereditary, it would be more likely that your son's hives were caused by an allergy if you or his father had allergies, asthma, or eczema. If the doctor thinks an allergy is likely, she might recommend allergy testing which involves skin tests and blood tests. Your son is not too young—these can be done at any age. If an allergy is identified, it's important that you make every effort to avoid the cause in the future in order to prevent hives and other more serious allergic reactions.