Alternate Names: Hives
Causes and Risks: About 1 out of 5 people experience urticaria (hives) at some time. Hives are more common in people who have experienced other allergic reactions, including hay fever and angioedema. The welts occur on the surface of the skin, usually in batches. Release of histamine and other chemicals into the bloodstream, associated with the allergic response, causes the itching, localized swelling, and other symptoms.
Many substances, called allergens, can trigger an allergic response resulting in hives. Common allergens include:
- medications
- foods (such as berries, shellfish, fish, nuts, eggs, milk, and others)
- pollen
- animal dander (especially cats)
- insect bites
- exposure to water, sunlight, cold or heat
- emotional stress
Hives may also develop after infections or illness (including autoimmune diseases, leukemia, and others). There seems to be a hereditary tendency toward the development of hives.
Some nonallergic causes of hives include:
Prevention: Avoid exposure to substances that are a known allergen for you.
Take only prescribed medications.
Avoid hot baths or showers after an episode of urticaria to prevent recurrence.
Symptoms:
- itching (pruritus)
- swelling of the surface of the skin into red or skin colored welts (wheals) with clearly defined edges
- sudden onset
- rapid resolution
- welts blanch to touch
- new welts develop when the skin is scratched
- welts enlarge, spread or join together to form large flat raised areas
- welts change shape, disappear and reappear within minutes or hours
Signs and Tests: The diagnosis is primarily based on the appearance of the skin, and is confirmed by a history of exposure to an irritant or allergen. Occasionally, skin tests for allergy may be performed.
Treatment: Hives in the throat may obstruct the airway, so any swelling in the throat or difficulty breathing with hives are emergency symptoms. Treatment may not be needed if hives are mild, and they may disappear spontaneously.
Antihistamines, adrenaline (epinephrine), terbutaline, cimetidine, corticosteroids, sedatives, or tranquilizers may reduce the inflammation, itching, and swelling.
Self care:
Cool compresses or soaks to the area may reduce swelling and pain. Avoid irritation of the area, and don’t wear tight clothing (which may trigger a new outbreak). Avoid known allergens to prevent recurrence of hives.
Prognosis: Hives may be uncomfortable, but they generally are harmless and disappear on their own.
Complications:
Call your health care provider if urticaria is severe and does not respond to treatment.
Call your health care provider or go to the emergency room if there is difficulty breathing, severe wheezing, or if fainting occurs.
