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. Medical professionals refer to hives as urticaria.

This article does not refer to an uncommon and more serious condition, hereditary angioedema. Hereditary angioedema involves swelling over the entire body, including some internal organs.

Hives and angioedema are reactions of the skin to the release of histamine or other chemicals into the blood. This is often, although not always, due to an allergic reaction.

There are many causes of hives and angioedema. At least half the time, the specific cause cannot be determined. Some of the more common triggers are the following. Infections such as viral illnesses, especially in children. Allergies to food, medications, cosmetics, soaps, and detergents.

Also, insect stings and bites, transfusions of blood or blood products and emotional and physical stress. Physical agents such as sunlight, heat, cold, water, or pressure. Chronic hives is a case of hives that lasts longer than 6 weeks. This can happen to anyone, but it is most common in women aged 40-60 years. Chronic hives can last for months or even years, but this is unusual.

Risk factors for hives and angioedema include the following. A previous case of hives or angioedema, a previous allergic reaction, and family members who have hives or angioedema.

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 usually appear first on the covered areas of the skin such as the trunk and upper parts of the arms and legs. 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.