Urticaria (hives) is a common skin condition affecting up to 40% of Americans at least once in their lifetime.  Urticaria can last from hours to years.  However, 85% of cases clear within six weeks.  They can occur at any age and may be recurrent.  They are red itchy raised swellings of varying sizes from tiny to the size of your palm or larger.  They can form rings with raised red borders and pale centers, can be solid red, and can have a variety of shapes.  They can occur anywhere on your body, scalp to toes.  A major characteristic of hives is that they rapidly change shapes, size, and location, often disappearing in one area within hours and popping up somewhere else.  Urticaria which is deeper under the skin is called angioedema.  Angioedema may particularly affect your feet, hands, eyes, lips, tongue, and sometimes throat.  Rarely, angioedema may be inherited.

Urticaria is caused by release of histamine and other similar substances from protective cells in your skin called mast cells.  The histamine causes fluid to leak from blood vessels, which causes the swellings or hives.  The fluid is rapidly absorbed and the hive goes away.  Hives usually stay on the skin, where they are irritating but not serious.  Occasionally, however, the swelling can occur in an area like the throat that can cause a medical emergency.  If you feel that your throat is closing, that you are having trouble breathing, or that you may pass out, call 911 immediately.

Hives can be triggered by a wide variety of substances, including pets, pollen, food, prescription or over the counter medications, insect bites, cosmetics, and cleaning products.  They can also be caused by physical triggers such as exercise, heat, cold, vibration, and stress.  Sometimes your skin becomes sensitive enough that you can “write” on it.  This is called dermatographia.  Occasionally hives can be caused by infection, especially viruses, or other medical illnesses such as autoimmune diseases.

If you are having hives or angioedema, please call your allergist, who can help you determine what might be the trigger and can prescribe medication for symptom control.


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