Causes

Some people know that certain foods or medications give them hives. For others, the causes may not be obvious.

Some foods that occasionally cause hives are nuts, eggs, beans, chocolate, berries, tomatoes, seasonings (mustard, ketchup, mayonnaise, spices), fresh fruits (especially citrus fruits), corn, fish and shellfish, milk, wheat, and cheese.

Medications that have been known to cause hives include penicillin, sulfa antibiotics, and codeine. If you develop hives shortly after you begin taking a new medication, stop taking it immediately and call your doctor.

Symptoms

Some hives look like mosquito bites. They often come in groups, and they may be as small as pencil erasers or as large as 2 or 3 inches across.

Acute hives (hives that are a reaction to something specific, such as a medication) can last for hours or days. Chronic hives (often of unknown cause) can last for weeks or months.

Extensive outbreaks of hives can be very serious, such as when hives form on the lips and in the throat, interfering with breathing and swallowing. Shock—in which severe swelling, dizziness, and even loss of consciousness occur—can accompany widespread hives.

Self-Care

• Try to determine the source of your hives so you can prevent a reaction in the future.
• Take an oral antihistamine, such as Benadryl or Chlor-Trimeton. Read the directions and warnings on the label carefully; these medications may make you drowsy.
• Rub ice directly over the hives or take a cool shower for temporary relief from itching.
• Soak in a lukewarm or cool bath with 1 cup of baking soda or an oatmeal product such as Aveeno.
• If hives develop after a bee sting or other insect bite, call your doctor or the emergency room.