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Urticaria,
also known as hives, is an outbreak of swollen, pale red bumps
or patches (wheals) on the skin that appear suddenly -- either
as a result of the body's adverse reaction to certain allergens,
or for unknown reasons.
Hives
usually cause itching, but may also burn or sting. They can
appear anywhere on the body, including the face, lips, tongue,
throat, or ears. Hives vary in size (from a pencil eraser
to a dinner plate), and may join together to form larger areas
known as plaques. They can last for hours, or up to three
to four days before fading.
Angioedema
is similar to urticaria, but the swelling occurs beneath the
skin instead of on the surface. Angioedema is characterized
by deep swelling around the eyes and lips and sometimes of
the genitals, hands, and feet. It generally lasts longer than
urticaria, but the swelling usually goes away in less than
24 hours.
Occasionally,
severe, prolonged tissue swelling can be disfiguring. Rarely,
angioedema of the throat, tongue, or lungs can block the airways,
causing difficulty breathing. This may become life threatening.
What Causes
Hives and Angioedema?
Hives
and angioedema form when, in response to histamine, blood
plasma leaks out of small blood vessels in the skin. Histamine
is a chemical released from specialized cells along the skin's
blood vessels.
Allergic
reactions, chemicals in foods, insect stings, sunlight exposure,
or medicines can all cause histamine release. Sometimes it's
impossible to find out exactly why hives have formed.
There
are several different types of hives, including:
Acute
urticaria: Hives lasting less than six weeks. The most common
causes are foods, medicines, latex, or infections. Insect
bites and internal disease may also be responsible.
The most
common foods that cause hives are nuts, chocolate, fish, tomatoes,
eggs, fresh berries, and milk. Fresh foods cause hives more
often than cooked foods. Certain food additives and preservatives
may also be to blame.
Medicines
that can cause hives and angioedema include aspirin and other
nonsteroidal anti-inflammatory medications such as ibuprofen,
high blood pressure medications (ACE inhibitors), or painkillers
such as codeine.
Chronic
urticaria and angioedema: Hives lasting more than six weeks.
The cause of this type of hives is usually more difficult
to identify than those causing acute urticaria. For more than
87% of people with chronic urticaria, the cause is unknown.
Chronic
urticaria and angioedema can affect other internal organs
such as the lungs, muscles and gastrointestinal tract. Symptoms
include muscle soreness, shortness of breath, vomiting, and
diarrhea.
Physical
urticaria: Hives caused by direct physical stimulation of
the skin -- for example, cold, heat, sun exposure, vibration,
pressure, sweating, and exercise. The hives usually occur
right where the skin was stimulated and rarely appear anywhere
else. Most of the hives appear within one hour after exposure.
Dermatographism:
Hives that form after firmly stroking or scratching the skin.
These hives can also occur along with other forms of urticaria.
This is considered a normal skin condition.
How Are
Hives and Angioedema Diagnosed?
Your doctor
will need to ask many questions in an attempt to find the
possible cause. Since there are no specific tests for hives
-- or the associated swelling of angioedema -- testing will
depend on your medical history and a thorough examination
by your primary care doctor or dermatologist.
Skin tests
may be performed to determine the substance that you are allergic
to. Routine blood tests are done to determine if a system-wide
illness is present.
How Are
Hives and Angioedema Treated?
The best
treatment for hives and associated swelling is to identify
and remove the trigger, but this is not an easy task. Antihistamines
are usually prescribed by your doctor or dermatologist to
provide relief from symptoms. Antihistamines work best if
taken on a regular schedule to prevent hives from forming
in the first place.
Chronic
hives may be treated with antihistamines or a combination
of medications. When antihistamines don't provide relief,
oral corticosteroids may be prescribed.
For severe
hive or angioedema outbreaks, an injection of epinephrine
(adrenaline) or a cortisone medication may be needed.
How Can
Hives Be Managed?
While
you're waiting for the hives and swelling to disappear, here
are some tips:
Avoid
hot water; use lukewarm water instead.
Use gentle, mild soap.
Apply cool compresses or wet cloths to the affected areas.
Try to work and sleep in a cool room.
Wear loose-fitting lightweight clothes.
When Should I Call the Doctor?
If hives
or angioedema occur with any of the following symptoms, contact
your doctor right away:
Dizziness
Wheezing
Difficulty breathing
Tightness in the chest
Swelling of the tongue, lips, or face
Reviewed
by the doctors at The Cleveland Clinic Department of Pulmonary,
Allergy and Critical Care Medicine.
Edited
by Charlotte E. Grayson, MD, Feb. 2004, WebMD.
Portions
of this page © The Cleveland Clinic 2000-2004
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