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Urticaria (Hives) What
is urticaria? 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. 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 certain foods and additives, infections,
drugs (including aspirin), cold, insect stings, alcohol, exercise, endocrine
disorders and emotional stress. In
some people, pressure caused by belts and constricting clothing causes hives.
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 physician and
sometimes, forbearance on the part of the patient. 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. In some cases you may
require blood tests to try and determine the cause. Allergy skin tests are
usually performed, as they often provide useful information. Your allergist-immunologist will decide
which tests to order based on your history and the suspected cause. What are the
different types of urticaria? They can be classified
into two categories: immunologic (allergic)
and non-immunologic. Immunologic
urticaria is the least common form.
It is caused by the immune’s system’s over-reaction 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-immunologic urticaria are those types of urticaria where a clear-cut allergic basis
cannot be proven. These take many
forms: ·
Dermographism is urticaria that develops when the skin is stroked with a firm
object. ·
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. ·
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. ·
Pressure urticaria
develops from the constant pressure of constricting clothing such as sock
bands, bra straps, belts or other tight clothing. Some cases of non-immunologic
urticaria may be caused by certain food additives such as artificial and
natural colors, sulfites, preservatives and others. In many cases,
particularly in chronic urticaria, the trigger for the problem can’t be
found; in this instance it is called idiopathic urticaria. If you have any more questions, your allergist-immunologist will
be happy to answer them. Hive Diet Allergy skin testing is
highly reliable for food allergies related to milk, eggs, nuts, fish and
other “whole” foods. However, with few exceptions, there is no available
allergy testing for food colors, preservatives, and artificial flavors. In order to evaluate the
possibility that your hives are related to a “hidden” food allergy, the only
practical way is to proceed with an elimination diet. This involves not
eating most “processed” foods including most deli items. You will need to read
labels so you can avoid eating foods that contain any artificial colors,
artificial flavors, preservatives especially citric acid, BHA and BHT, and
nitrates or nitrites often found in deli meats. It is generally best to
spend at least 1 day reviewing what you commonly eat at home to determine
which foods will need to be “eliminated”. Then spend another day shopping for
foods that are “safe” to eat. While on the elimination diet you should not
eat out. This diet should be strictly followed for a minimum of 5 days. If after 5 days there has
been no improvement in the hives, then a “hidden” food allergy is not the
underlying cause. If your hives did dramatically improve, then there indeed
may be a “hidden” food allergy. At this point we would slowly add back one
food at a time to narrow down the cause. |