To identify food allergies, a doctor first records a
detailed medical history. The patient will usually keep
a food diary documenting exactly what is eaten and
when. The patient will also record any physical symptoms
and when they occur. In most cases, patterns of
reaction to specific foods can be seen in the food diary.
Other means of diagnosis food allergies includes
Blood tests (RAST, CAP–RAST)—A sample of
blood is drawn and sent to the lab. These tests measure
antibodies in the blood. These antibodies form in
response to specific foods. These antibodies occur
after the body has been exposed to a food and has become allergic. This test measures IgE which is
specific for each food. Individual food allergies may
be identified by this test.
Skin Tests—In a skin allergy test, a small amount of
extract of a food that is suspected of causing an
allergic reaction is placed on the skin, the skin is
scratched in that area, and observed for reaction. If
an allergy exists, a small bump (similar to a mosquito
bite) will appear usually within 15 minutes. This is a
rapid way to see if a food allergy exists.
Food Challenge—This is a food test in which neither
the testing doctor nor the patient knows what food is
given. Opaque capsules are filled (by an assistant or
another doctor) with foods that are suspected of causing
allergies and foods that are not. The capsules
prevent the patient from tasting or smelling the food.
The patient swallows a capsule, and the doctor
observes to see if a reaction occurs.
This teat is not
appropriate a person who has had a severe allergic
reaction. It is time consuming and is usually performed
when a doctor suspects the allergic reaction
is not being caused by food. The test can rule out food
as a cause for allergic reactions.
After a food allergy is diagnosed, an elimination
diet may be implemented. Avoiding foods that cause
allergic reaction may sound simple, but it can be quite
difficult. It is easy to avoid eating scrambled eggs or a
handful of raw peanuts; however, many common food
allergy foods are ingredients in many foods.
