Understanding Hives (Urticaria)

Urticaria (hives) are red, itchy, and swollen areas on the skin. They are most often an allergic reaction from eating a food or taking a medicine. Sometimes the cause may be unknown. A single hive can vary in size from a half inch to several inches. Hives can appear all over the body. Or they may appear on only one part of the body.

What causes hives?

Hives can be caused by food and beverages such as:

• Tree nuts (almonds, walnuts, hazelnuts)

• Peanuts

• Eggs

• Shellfish

• Milk

Hives can also be caused by medicines such as:

• Antibiotics, especially penicillin and sulfa-based medicines 

• Anticonvulsant or antiseizure medicines 

• Chemotherapy medicines 

Other causes of hives include:

• Infection or virus

• Heat

• Cold air or cold water

• Exercise

• Scratching or rubbing your skin, or wearing tight-fitting clothes that rub your skin

• Being exposed to sunlight or light from a light bulb, in rare cases

• Inhaled-chemicals in the environment from foods and drugs, insects, plants, or other sources

In some cases, hives may occur again and again with no specific cause.

If you have hives

• Stay away from the food, drink, medicine, or other thing that may be causing the hives.

• Ask your healthcare provider how to control itchy or irritated skin.

• Talk with your healthcare provider right away if you think a medicine gave you hives.

Watch for anaphylaxis

If you have hives, watch for symptoms of a severe reaction that can affect your entire body. This is called anaphylaxis. Symptoms can include swollen areas of the body, wheezing, trouble breathing or swallowing, and a hoarse voice. This reaction may happen right away. Or it may happen in an hour or more. In extreme cases, the airways from mouth to lungs may swell and make breathing difficult. This is a medical emergency. Use epinephrine medicine if you have it, and call 911 or go to the emergency room.