Hives (Urticaria & Angioedema)
Table of Contents
- Hives facts
- What are hives (urticaria) and angioedema? What do hives look like?
- What causes hives and angioedema?
- What are the different kinds of hives?
- What are the signs and symptoms of ordinary hives?
- What are the causes of ordinary hives?
- What are the causes of chronic hives?
- Are there other conditions that mimic hives?
- What is the treatment for hives?
- What is the prognosis of hives?
What causes hives and angioedema?
Hives appear when histamine and other compounds are released from cells called mast cells, which are normally found in the skin. Histamine causes fluid to leak from the local blood vessels, leading to swelling in the skin.
Hives are very common. Although annoying, hives usually resolve on their own over a period of weeks and are rarely medically serious. Some hives may be caused by allergies to such things as foods, infections, medications, food colors, preservatives and insect stings, and contactants; but in the majority of cases, no specific cause for them is ever found. Although patients may find it frustrating not to know what has caused their hives, maneuvers like changing diet, soap, detergent, and makeup are rarely helpful in preventing hives unless there is an excellent temporal relationship.
Having hives may cause stress, but stress by itself does not cause hives.
What are the different kinds of hives?
Hives fall into two chronological categories: acute urticaria (ordinary hives which resolve after six to eight weeks) and chronic urticaria (which continue longer than six to eight weeks). Since hives are so common and acute urticaria by definition resolves spontaneously, physicians do not generally expend much time or expense to evaluate the cause of hives of less than eight weeks duration.