Allergies and Hives (Urticaria and Angioedema) Hives, also known as urticaria, are an outbreak of swollen, pale red bumps, patches, or welts on the skin that appear suddenly -- either as a result of allergies, or for other reasons.

Hives usually cause itching, but may also burn or sting. They can appear anywhere on the body, including the face, lips, tongue, throat, or ears. Hives vary in size (from a pencil eraser to a dinner plate), and may join together to form larger areas known as plaques. They can last for hours, or up to several days before fading.

Angioedema is similar to hives, but the swelling occurs beneath the skin instead of on the surface. Angioedema is characterized by deep swelling around the eyes and lips and sometimes of the genitals, hands, and feet. It generally lasts longer than hives, but the swelling usually goes away in less than 24 hours.

Occasionally, severe, prolonged tissue swelling can be disfiguring. In rare cases, angioedema of the throat, tongue, or lungs can block the airways, causing difficulty breathing. This may become life-threatening.