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Types of Allergy Tests
It used to be if you wanted to
find out what you were allergic
to you had to undergo a long
series of tests that could take
weeks or months. If you were
allergic to something unusual or
rare it could take years or,
more commonly, you never would
find out. If your allergies were
seasonal, they probably
disappeared before the testing
clinic found an answer and you
would give up on the clinic
testing and go back to life as
before. Much of that procedure
today has been speeded up and is
more straightforward but if you
are being checked for allergies
there will probably still be
several types of tests
performed.
There are three basic ways that
a clinic or hospital can use to
test you for allergies. The most
commonly used is a skin test.
This involves putting a small
amount of the allergen on your
skin. Allergen, by the way, is
the medical term for the
substance suspected of causing
your allergy. Most often, the
allergen is applied to your
forearm but it could also be
done on your back or upper arm.
Then the skin in that area is
irritated by pricking it with a
needle or scratching the skin.
This allows the substance to get
under your skin. If you are
allergic to it there will
usually be an allergic reaction
in less than 10 to 15 minutes.
Usually the reaction just
involves redness, itching and
swelling of the skin but testers
have to be careful with skin
tests because in some cases the
reaction may be severe and
involve respiratory
complications. A variation of
the skin test is the intradermal
allergy test. This test uses a
small needle to inject the
allergen just beneath the skin.
Skin tests are usually used to
identify things in the air that
you inhale that might be causing
your allergy or allergies to
insect or animal bites.
A second type of allergy testing
is called elimination testing.
This is most often used to
identify food and diet
allergies. In a very controlled
environment, various foods are
either added or removed from
your diet and your reaction is
monitored. Often the food is
disguised in some fashion to
prevent psychological factors
from interfering with the test.
Sometimes if you think you are
allergic to something you
abnormally influence the result.
Obviously, this method is very
time consuming and can only be
used if the reactions are
relatively mild.
The third and perhaps the best
method of allergy testing is the
blood test. As the name implies,
this involves taking a small
sample of your blood and sending
it off for laboratory testing.
The lab procedure is complicated
but basically, they will expose
your blood to various allergens.
If you are allergic, your blood
will create what are called IgE
antibodies to fight off the
allergen. Depending on what kind
of IgE antibodies are created
and how many are created the lab
can both identify your allergy
and tell you how severe it is.
RAST and UniCAP are the two main
specific types of modern blood
testing for allergies. UniCAP is
almost a fully automated
procedure that can check for
several 100 allergens and will
even assign a number from 1 to 6
to identify the severity of the
allergic reaction. The major
disadvantage of blood testing is
it requires specialized
equipment. Usually your clinic
or hospital will have to mail
the blood sample off and will
not get results back for several
weeks.
Michael Russell Your Independent
guide to
Allergies