Ask the experts
Hives (urticaria) are raised, red spots on the skin that often itch. Hives are usually indicative of an allergic reaction. Hives are a common reaction in people who have allergies. A number of substances can trigger an outbreak of hives, including foods, medications, pollen, animal dander, or insect bites.
Hives can also develop as a result of sun or cold exposure, infections, excessive perspiration, and emotional stress. The reason why stress seems to precipitate an outbreak of hives in many people is not completely understood but is likely related to the known effects of stress on the immune system. In many cases, the cause of hives in a given individual cannot be identified.
If you aren't certain what is causing your hives and are bothered by the symptoms, talking to your can help you identify potential allergic triggers. He or she can also order blood or skin tests for allergies if necessary.
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care