Contact your health care provider or return to the hospital if you have any of the following, rash or swelling returns or gets worse, difficulty with your medicines, new symptoms, sores or swelling of the mouth, tongue, or throat, fever or chills, difficulty with breathing or swallowing, and vomiting or diarrhea.

Avoid exposure to any food, medicine, or physical agent that has been identified to cause your hives or angioedema. Reducing emotional and physical stress may help. In rare cases, you may need to take antihistamines or other medicines for an extended time to prevent further hives or swelling.

Hives and angioedema may be very uncomfortable but will not cause serious harm. The hives will not leave scars. Most people do well with treatment. Hives and angioedema usually will last only a few hours to a few days. Chronic hives lasts longer than 6 weeks but is rare.

Hives is a rash of smooth, raised, pink or reddish bumps of different sizes called wheals that comes on suddenly. The wheals look something like mosquito bites. They may cover all or part of the body and are usually very itchy. Hives are usually patchy at first, but the patches may run together until the hives cover most of the body. Hives usually appear first on the covered areas of the skin such as the trunk and upper parts of the arms and legs.

The patches can be small or large. They are usually irregular in shape. Often, the patches have clearing of the redness in the center with a red halo or flare at the edges. Wheals appear in batches. Each wheal may last from a few minutes to 6 hours. As wheals disappear, new ones form. A case of hives usually lasts at most a few days.

Other, more severe allergic reactions may occur with hives or angioedema. A reaction may start with hives or angioedema and then progress rapidly to more serious symptoms. The most serious reactions, which can be life-threatening emergencies, are called anaphylactic reactions.

Angioedema is like hives, only the welts are larger and form at a deeper layer in the skin. This causes severe swelling, usually in the face, near the eyes and mouth. The swelling can also occur in the inside of the throat, which is a dangerous situation because it can close off the passage of air into the lungs.

Hives and angioedema can occur together, but they usually do not. Hives is the most common rash for which people seek emergency medical care. One of every 5 people will have hives at some time in their lives. Angioedema is less common. Hives and angioedema can happen at any age.