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Urticaria and Angioedema

Urticaria and Angioedema


Updated May 30, 2014

Urticaria and Angioedema

Urticaria develops when histamine is released into the small blood vessels (capillaries). The capillaries dilate which causes a welt, and fluid oozes into the surrounding tissue, causing swelling. Histamine also causes intense itching.

Updated May 30, 2014

What is Urticaria and Angioedema?

Urticaria, commonly known as hives, is a distressing disorder affecting up to 20 percent of the population at some point in their lives. The swelling that sometimes accompanies urticaria, called angioedema, can lead to swelling of the face, hands and feet.

The rash of urticaria is usually bumpy, red and itchy. The bumps can be the size of mosquito bites to coin-size or larger, and can group together into irregular shapes. The rash will tend to come and go within a few hours, moving from one place on the body to another.

Angioedema, on the other hand, is usually not red or itchy, but tends to sting and burn, and can be described as “numbness.” This swelling can be severe, and if it affects a person’s ability to breathe, can be life-threatening.

Both urticaria and angioedema are a result of histamine and other chemicals released from mast cells in the skin and mucous membranes. This may occur through an allergic process or one in which mast cells release chemicals without IgE being involved.

Categories of Urticaria and Angioedema

Cases of urticaria and angioedema can be acute, lasting less than 6 weeks, or chronic, lasting more than 6 weeks. The length of symptoms can often be a clue as to the cause of the symptoms. For example, the most common cause of acute urticaria and angioedema in children is viral infections. Other common causes of acute symptoms include allergies (typically foods, medications, contact with animal dander and insect stings and bites), stress, and infections such as the common cold and strep throat.

Unlike acute urticaria, only about 5 to 10 percent of chronic urticaria and angioedema are caused by allergies. Chronic cases are much more likely to be related to auto-immune causes than allergies. In the autoimmune form of urticaria and angioedema, a person makes antibodies against a component of their mast cells, triggering the release of histamine and causing symptoms.

Other forms of chronic urticaria include the physical urticarias, in which the rash is triggered by stimuli such as heat, cold, sunlight, pressure and vibration. It is important to note that many forms of urticaria get worse with heat (such as from hot baths, exercise or wearing too much clothing) and pressure (such as around tight waistbands from clothing).

Lastly, some forms of urticaria and angioedema are related to other diseases, such as other auto-immune diseases (such as lupus and rheumatoid arthritis), certain cancers, chronic infections such as viral hepatitis, and some hereditary forms.

How to Identify the Cause of Urticaria

In acute forms of urticaria and angioedema, a history of the events surrounding the outbreak is the most important information that can be obtained:
    • Was there a specific food eaten or medication taken within minutes to hours before the symptoms started?
    • Was the person stung or bitten by an insect shortly before the rash began?
    • Had the person been ill from an infection, or had more stress in their life recently?
Unless there is information suggesting a specific cause, performing allergy testing is not usually needed for acute urticaria.

In chronic cases, a physician may check various blood and urine tests, and other procedures such as X-rays to look for other causes. If a physical urticaria is suspected, special tests to mimic the physical stimulus may be performed, such as placing an ice cube on the skin to cause a hive to form in people with cold urticaria. It is important to note that in most cases of chronic urticaria and angioedema, a specific cause is never found, and is termed “idiopathic.”

How Urticaria is Treated

The main treatment for urticaria is with antihistamines. These are usually given in oral forms, and may need to be given in large or frequent doses to control the symptoms. Short courses of corticosteroids may be needed, and rarely, if the symptoms are severe, epinephrine shots can be used for immediate, but temporary, relief.

If the cause of the urticaria is known or suspected, such as a food or medication, avoidance of this trigger may resolve the symptoms. In cases of chronic idiopathic urticaria, triggers such as acute infections of any kind (such as the common cold), stress, and use of non-steroidal anti-inflammatory medications (aspirin and ibuprofen, for example), may flare the symptoms.

In most cases of chronic urticaria and angioedema, symptoms last less than a few months to a few years. Some people may experience symptoms for many years, and those who do should be seen by an allergist for an appropriate testing and treatment.

Want to keep learning? Find out about the two most common types of physical urticaria:

Source: Practice Parameters for Disease Management: Acute and Chronic Urticaria and Angioedema. Ann Allergy. 2000; 85: S525-44.

DISCLAIMER: The information contained in this site is for educational purposes only, and should not be used as a substitute for personal care by a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition.

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