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Frederick R. Jelovsek MD, MS
When your nose is runny and eyes are itchy you
probably are just interested in relief; not in why
this reaction is happening. Sometimes though, it
is helpful to know the detail of how a medical
condition is produced especially when it is one
that is chronic and going to afflict you the rest
of your life. Allergy is one such condition.
People with allergies have genes that make them
more likely to develop a bodily reaction to
various substances they are exposed to.
The body's immune system is the main protective
mechanism to maintain health. It identifies and
fights off bacteria, viruses, parasites, cancer
cells, food and any foreign protein substance.
Lymphocytes are one type of white cell in your
blood and they are a major component of the immune
system. As soon as a foreign protein enters the
body, the lymphocytes identify the protein,
fingerprint it and determine if it belongs to this
body or not. "Lymphocytes act like traveling
customs agents. Everywhere they go, they are busy
checking the passports of every cell they
encounter. Whenever they discover a cell that
seems threatening, they immediately begin
countermeasures against it. The biochemical
process behind these countermeasures is amazing!
(1)
Allergies result when this immune system is
hypersensitive, overreactive. When the system
misidentifies harmless proteins as serious enemies
and then reacts out of proportion to the threat,
you get symptoms from this major bodily battle.
Those symptoms may be mildly annoying or a major
illness. Usually for your immune system to
overreact like this you must have a genetic
tendency for it.
After the lymphocyte identifies the foreign
protein (antigen) it goes back to a lymph node
where it changes into a different type of white
blood cell (mast cell). The mast cell manufactures
a chemical called an immunoglobulin that is
exactly configured like a laser ray to destroy the
specific protein that the lymphocyte identified in
the first place. Of the different immunoglobulins
(IgA, IgD, IgE, IgG, IgM), Ig E is the class that
forms an allergic reaction. They attach to other
white blood cells in what is called the
sensitizing exposure,
When the protein comes into the body again, at
least 7-10 days after the sensitizing reaction,
the IgE primed mast cells release many chemicals
including histamine that try to destroy the
"invading" protein. Histamine lowers the local
blood pressure and causes itching and swelling .
It can also cause wheezing, an itchy, runny nose,
nausea, vomiting or diarrhea. That is why "anti-
histamine" drugs are used to treat allergies.
Specific allergies can be identified either by a
blood test for IgE or by a scratch test in which
the suspected allergen is "scratched" into the
skin to see if the body reacts to it with redness
and swelling. A problem with specific
identification of allergies, however is what is
called cross-reactivity. Sometimes proteins of
different but similar substances, e.g., shrimp and
crab meat, can both cause an allergic response
even though the body had previously been exposed
to only one of them. Even so, allergen
identification is very important so that you can
avoid the offending allergen in the first place.
Now why is it important to know the mechanism of
action for allergies? If there is a genetic
disposition for your body to form allergic
responses, there is not much you can do - correct?
No. You basically have two practical choices for
self-care. Identify the causative agents so you
absolutely avoid them and treat with anti-
histamines for mild but annoying allergic
reactions. Fortunately there is a self
home test for food allergies, Food allergy test kit, and also one that tests for grasses, molds, dust and cat allergies along with some common food allergies such as milk, eggs and wheat, MyAllergyTest. For other tests you will have to have a doctor's
order and have a blood drawn and sent to a special
laboratory. If you are having serious reactions,
see an allergist for allergen identification and
treatment.
One last tip. The gold standard for diagnosing
allergies are the scratch test sets applied in the
allergist's office. Many times, however, you may
not want to suffer the reactions you get during
testing or you may fear causing a new allergy by
sensitizing through your skin to a new substance
you are not already allergic to. The allergy
doctor may prefer the scratch tests because they
are more accurate but you can ask to have the
blood test done instead, with subsequent scratch
testing if needed, to narrow down the specific
allergen from a general group of substances.
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