At some point, about one in five people comes down with a case of raised, red, itchy welts that appear suddenly in one spot or across the body. The condition, called hives or urticaria, can last for a few days or a few weeks, and the bumps or welts can range in size from a pencil eraser to a dinner plate.

A variety of factors, such as allergies, stress, and reactions to foods or prescription or over-the-counter drugs, can trigger an outbreak. Extreme heat, perspiration, or exposure to the cold can also bring on hives. One of these stimuli can cause the body to release the chemical histamine, which sets off a series of inflammatory reactions. As a result, blood plasma leaks between small blood vessels in the skin, resulting in fluid-filled bumps. In one outbreak, hives can appear and disappear multiple times.

In the vast majority of cases, the welts go away on their own without any side effects. But in rare, severe cases, the swelling may lead to difficulty breathing or swallowing, requiring medical attention. Symptoms are usually treated with an over-the-counter or prescription antihistamine; cold compresses and wearing loose clothing also help. But the only way to eradicate the condition entirely is to avoid the trigger. That’s why, for chronic cases, physicians often perform allergy tests, in which the skin is exposed to tiny amounts of potential causes. Once the offending substance is identified, patients know to steer clear of it.

ADDITIONAL FACTS

  1. The most common food triggers of hives include nuts, chocolate, shellfish, tomatoes, eggs, berries, milk, and food additives and preservatives.
  2. A related condition is called angioedema, in which the swelling occurs beneath the skin instead of on its surface.