|
The
skin prick test or a blood test, such as the RAST (or
radioallergosorbent test), is commonly used to begin to
determine if an allergy exists. (The RAST is sometimes
called the CAP-RAST or ImmunoCap test.)
A
skin prick test is usually less costly and can be done
in the doctor's office. The doctor places a drop of
the substance being tested on the patient's forearm
or back and pricks the skin with a needle, allowing
a tiny amount to enter the skin. If the patient is allergic
to the substance, a wheal (mosquito bite-like bump)
will form at the site within about 15 minutes.
A
RAST test requires a blood sample. The sample is sent
to a medical laboratory, where tests are done with specific
foods to determine whether the patient has IgE antibodies
to that food. The results are usually received within
one week.
Which
test is better?
Although
both tests are reliable, there are instances where one
is better than the other. Many doctors use a RAST for
young children or for patients who have eczema or other
skin problems that would make if difficult to read the
results of a prick skin test. The results of either
test are combined with other information, such as a
history of symptoms and a food challenge, to determine
whether a food allergy exists.
|
