Urticaria,
commonly known as hives, usually strikes suddenly. First the skin
itches, then it erupts into red welts. The itching may be severe,
keeping people from working or sleeping. It's a distressing disorder
which affects an estimated 20 percent of the population at one
time or another in their lives.
What
is urticaria?
Most cases of urticaria are acute, lasting from a few hours to
less than six weeks. Some cases are chronic, lasting more than
six weeks. The welts may appear in one place, disappear after
a short time, then erupt at another spot, then another. They are
made worse by scratching. Each individual hive lasts no more than
24 hours.
What
kinds of things can trigger attacks of urticaria?
Bouts of urticaria have been traced to such triggers as infections,
drugs (including aspirin), certain foods and additives, cold,
sun exposure, insect stings, alcohol, exercise, endocrine disorders
and emotional stress. In some people, pressure caused by belts
and constricting clothing causes eruption. Urticaria may be a
response to infection including the common cold, strep throat
and infectious mononucleosis.
In the urticaria-prone
person, these triggers cause the body to release chemical mediators,
including histamine, from cells. Histamine (which causes itchy,
runny noses and watery eyes in hay fever sufferers) dilates the
walls of blood vessels, allowing fluids to leak out into the surrounding
tissues. Swelling and itching are the result.
How
are urticaria "triggers" identified?
In some cases, the trigger is obvious - a person eats strawberries
or shrimp, then develops urticaria within a short time. But because
there are so many possible causes for urticaria, other cases require
determined detective work on the part of the patient and physician.
In some cases, the cause is never identified.
A single episode
of uncomplicated acute urticaria probably does not need formal
evaluation. Patients with recurrent episodes of acute urticaria,
with chronic urticaria, or with urticaria complicated by swelling,
trouble breathing or other potentially serious problems, an evaluation
is recommended. See your regular physician first, in order to
evaluate for non-allergic causes of urticaria. If allergy is suspected,
keep a diary of foods eaten, any unusual exposures, and when you
have hives. Bring the diary with you to the allergist's office.
To unravel the urticaria puzzle, your allergist-immunologist will
take a detailed history, looking for clues in your lifestyle that
will help pinpoint the cause of your symptoms. You'll be asked
about the frequency and severity of your symptoms, your family's
medical history, medications you're taking, your work and home
environment, and miscellaneous matters. The allergist will want
to review your diary for further clues.
In some cases
you may require tests to analyze blood and urine, and other procedures
such as x-rays. Skin testing may provide useful information in
some cases. Your allergist-immunologist will decide which tests
to order based on the different types of urticaria and the suspected
cause.
What
are the different types of urticaria?
They can be classified into two categories: allergic and non-allergic.
Allergic urticaria
is the least common form, although it is somewhat more common
in children than in adults. It is caused by the immune system's
overreaction to foods, drugs, infection, insect stings, blood
transfusions or other substances. Foods such as eggs, nuts and
shellfish, and drugs such as penicillin and sulfa are common causes
of allergic or immunologic urticaria. Recent studies also suggest
that some cases of chronic urticaria are caused by autoimmune
mechanisms, when the patient develops immune reactions to components
of his or her skin.
Non-allergic
urticaria are those types of urticaria where a clear-cut allergic
basis cannot be proven. These take many forms:
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Dermographism
is urticaria that develops when the skin is stroked with a
firm object. |
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Cold-induced
urticaria appears after a person is exposed to low temperatures
for example, after a plunge into a swimming pool or
when an ice cube is placed against the skin. |
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Cholinergic
urticaria, which is associated with exercise, hot showers
and/or anxiety, is a form of hives that is related to release
of certain chemicals from parts of the nervous system that
controls such body functions as blood pressure and heart rate.
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Pressure
urticaria develops from the constant pressure of constricting
clothing such as sock bands, bra straps, belts or other tight
clothing. |
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Solar
urticaria arises on parts of the body exposed to the sun;
this may occur within a few minutes after exposure. |
Some cases
of non-allergic urticaria may be caused by reactions to aspirin
and, possibly, certain food dyes, sulfites, and other food additives.
In many cases, particularly in chronic urticaria, the trigger
for the problem can't be found; in this instance it is called
idiopathic urticaria.
Certain types of urticaria are more painful than itchy, may go
away leaving a bruise on the skin, and individual hives may last
more than 24 hours. In such cases, and selected other situations,
a biopsy of the skin may be necessary for diagnosis.
How
is urticaria treated?
Your allergist first will prescribe medications, such as antihistamines,
to alleviate the discomfort. Severe, complicated attacks of urticaria
can be temporarily relieved by injections of epinephrine; rarely
in these cases, corticosteroids may be prescribed for a short
period. Other drugs may be required for specific types of urticaria.
If the cause
can be identified, the best course of treatment is avoidance of
the substance that triggers urticaria. If a problem with a specific
food is strongly suspected, then it should be avoided. This may
require a careful reading of packaged food labels and inquiry
about ingredient in restaurant meals. Persons with solar urticaria
should wear protective clothing and apply sunscreen lotions when
outdoors. Loose-fitting clothing will help relieve pressure urticaria.
Avoid harsh soaps and frequent bathing to reduce the problem of
dry skin, which can cause itching and scratching that can aggravate
urticaria. Vigorous toweling after a bath may precipitate hives.
Although success
of identifying the cause of chronic urticaria varies from clinic
to clinic according to patient populations, it usually is no higher
than 20 percent of cases. Chronic urticaria may last for months
or for years and burn itself out, never to bother the sufferer
again. If you have any more questions, your allergist-immunologist
will be happy to answer them.
For more
medical information, please contact an allergist
in your area.
