Hives (urticaria) and angioedema

Urticaria is an itchy rash consisting of inflamed wheals or welts that are raised above the level of the surrounding skin.  The wheals vary in size and shape, and tend to come and go within a period of less than 24 hours.  The whole lip or eyelid may swell when wheals involve them.  When this process involves the tissues under the skin, a more diffuse and extensive swelling known as angioedema may occur.  If this causes airway obstruction or is associated with a fall in blood pressure, the condition is termed anaphylaxis.  Eczema or atopic dermatitis is a different condition in which affected skin is usually rough and inflamed, remaining unchanged in appearance over several days.

Short-lived attacks of urticaria and/or angioedema may be caused by allergy to a food or a medication, and in young children may be provoked by infection.   In some cases the problem may be provoked by physical factors such as cold, scratching, pressure on the skin or sweating.  More rarely, exercise, heat, sunlight or mechanical vibration may provoke attacks.  Treatment for angioedema associated with urticaria is usually the same as the treatment for urticaria.

When the condition lasts for months it is the classified as chronic.  In these patients and in patients with recurring short-lived episodes, causes that are external to the body are rarely found.  Approximately one half of patients with chronic urticaria have been found to have an antibody in the blood that attacks mast cells in the skin and causes them to release their histamine.  Histamine, once released from mast cells, can make blood vessels leak fluid into and under the skin to cause swelling, and can stimulate pain-sensing nerves in the skin to cause itching.  The treatment includes use of two types of antihistamines, and for severe episodes, corticosteroids taken orally.

Angioedema without a history of urticaria can be caused by certain drugs (ACE inhibitors), certain malignancies, and by an inherited enzyme deficiency (C1 esterase inhibitor deficiency).   Symptoms of the hereditary enzyme deficiency problem typically include attacks of abdominal pain, vomiting, upper airway obstruction and visible non-itchy angioedema.  This relatively rare disease requires treatment different from that of chronic urticaria and angioedema.

Further Reading:
AAAAI:   Allergic skin conditions
American Academy of Dermatology:   Urticaria

Back

Disclaimer:   This site is for educational purposes only.  Any information that you have found in this web site is not intended to replace medical care or advice given to you by your own physicians. You should consider consulting your local medical library and other web sites for additional information. 

Comments and suggestions welcome!   Email: schumach@u.arizona.edu
Content Owner:  Michael J. Schumacher, MB, FRACP, The University of Arizona
Updated 1/2008