Urticaria - Hives
Hives are pale red swellings of skin
"wheals" that occur in groups on any part of the skin. Urticaria is
the medical word for hives. Each hive lasts a few hours before fading without
trace. New areas may develop as old areas fade. They can vary in size from as
small as a pencil eraser to as large as a dinner plate and may join together to
form larger swellings. Hives are usually are itchy, but may also burn or sting.
Hives are formed by blood plasma leaking out of
small blood vessels in the skin. This is caused by the release of a chemical
called histamine. Histamine is released from cells called "mast cells"
which lie along the blood vessels in the skin. Allergic reactions, chemicals in
foods, or medications can cause histamine release. Sometimes it's impossible to
find out why hives are forming.
Hives are very common -- 10-20 percent of the
population will have at least one episode in their lifetime. Hives usually go
away within a few days to a few weeks. Occasionally, a person will continue to
have hives for many years.
When hives form around the eyes, lips or
genitals, the tissue may swell excessively. Although frightening, the swelling
usually goes away in less than 24 hours.
Hives
lasting less than six weeks are caused by "acute urticaria". With this
type of hives, the cause can usually be found. The most common causes are foods,
drugs or infections. Insect bites and internal disease may also be responsible.
Other causes can be pressure, cold, and sunlight.
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. Food additives and preservatives may also be the
problem.
Hives may appear within minutes or up to two
hours after eating, depending on where the food is absorbed in the digestive
tract.
Almost
any prescription or over-the-counter medication can cause hives. Some of those
drugs include antibiotics, pain medications, sedatives, tranquilizers, and
diuretics. Antacids, vitamins, eye and ear drops, laxatives, vaginal douches, or
any other non-prescription item can be a potential cause of hives. If you have
an attack of hives, it's important to tell your doctor about all of the
preparations that you use to assist in finding the cause.
Many infections can cause hives. Colds are a
common cause in children.
Hives
lasting more than six weeks are called "chronic urticaria". The cause
of this type of hives is usually much more difficult to identify than that of
acute urticaria. In patients with chronic urticaria, the cause is found in only
a small number of patients. Your doctor will need to ask many questions in an
attempt to find the possible cause. Since there are no specific tests for hives,
testing will depend on your medical history and a thorough examination by your
dermatologist. Routine blood tests are of little or no value.
Hives can be caused by sunlight, cold, pressure,
vibration, or exercise. Hives due to sunlight are called solar urticaria. This
is a rare disorder in which hives from within minutes of sun exposure on exposed
areas and fade within one to two hours. Hives due to the cold are more common.
These appear when the skin is warmed after exposure to cold. If the cold is over
large areas of the body, large amounts of histamine may be released which can
produce wheezing, flushing, generalized hives, and fainting. A simple test for
this type of hives can be done by applying an ice cube to the skin.
These hives can form after firmly stroking or
scratching the skin "dermatographism". It affects about 5 percent of
the population. Most people with this condition are otherwise healthy. These
hives can also occur along with other forms of urticaria. If it is present along
with hives, finding and eliminating the cause usually clears the dermatographism.
Otherwise, it may last for months or even years.
The best treatment for hives is to find and
remove the cause. This is not an easy task. Antihistamines are usually
prescribed by your dermatologist to provide relief. Antihistamines work best if
taken on a regular schedule to prevent hives from forming. No one antihistamine
works best for everyone, so your dermatologist may need to try more than one or
different combinations to find what works best for you.
In severe hives, an injection of epinephrine
(adrenalin) or a cortisone medication may be needed.
