Hives — also known as urticaria (ur-tih-KAR-e-uh) — is a skin reaction that causes itchy welts, which can range in size from small spots to large blotches several inches in diameter. Hives can be triggered by exposure to certain foods, environmental allergies, medications or other substances.

Angioedema is a related type of swelling that affects deeper layers in your skin, often around your eyes and lips. In most cases, hives and angioedema are harmless and don’t leave any lasting marks, even without treatment.

The most common treatment for hives and angioedema is antihistamine medication. Serious angioedema can be life-threatening if swelling causes your throat or tongue to block your airway.