Food allergy testing is a way to check your body's reaction to certain foods. Along with a medical history and physical exam, one or more of the following tests may be done to see what foods you may be allergic to:
If you have a history of allergic symptoms after eating certain foods, your healthcare provider may recommend that you have tests to check for food allergies. This will help you know which foods you should avoid eating to prevent an allergic reaction.
You may need to be tested for food allergies if you have some of the following symptoms shortly after eating:
One or more of the following tests may be done.
Skin prick test: A skin prick test is often used to help identify food allergies. For this test, a drop of food extract is put on the skin and then the skin is pricked with a small needle through the drop of the food extract. The test can also be done with a pricking device that has been presoaked in the food extract. Only the top layer of skin is pricked. The test is usually done on your back or arm. The skin test is ready to check in about 15 minutes. You may be allergic to the food in the extract if a red bump that looks like a mosquito bite appears at the spot where the food extract was placed. This test by itself is not enough for diagnosis of a food allergy.
Blood test (RAST test): Blood tests are not done as often as skin prick tests, but they can be useful at times. The RAST test checks a sample of your blood for antibodies your body makes when it is trying to fight off allergy-causing substances in food (allergens). This test by itself is also not enough for a diagnosis.
Misleading results can occur with both skin and RAST tests. That is, the test may indicate that you are allergic to a food that further tests show you are not allergic to (false positive results). A food challenge test may be necessary to confirm the results.
Elimination diet: Your healthcare provider may ask you to stop eating foods you may be allergic to for a week or two. Then you will add the foods back into your diet one at a time. This process can help connect your symptoms to specific foods. During this time, you will need to keep a record of the foods you eat and any symptoms you have. If you have had a severe reaction to foods, this method cannot be used for diagnosis.
Food challenge: A food challenge test is the best way to diagnose a food allergy. The test is usually done in your healthcare provider’s office. Sometimes it is done in the hospital. To do the test, you are given gradually increasing amounts of a food--either in colorless capsules or in a slush or pudding--while your provider watches for symptoms. This test should be done only by a trained professional who is ready to treat you if you have a serious reaction to the food. If you have symptoms of an allergy after the challenge that fit with your medical history and other test results, the diagnosis can be made.
Ask your healthcare provider how you will get the result of your skin prick or blood test.
If the skin or blood test is negative for a food, then you probably do not have an allergy to that food.
If the skin test is positive for a certain food, it may mean you are allergic to that food.
Sometimes the test can be positive even if you are not allergic to the food. The positive test result can be wrong sometimes because:
Remember that test results are only one part of a larger picture that takes into account your medical history and current health. It’s important to confirm a suspected food allergy with careful testing and diagnosis. Many presumed food allergies are not really allergies. Talk to your healthcare provider about your test results and ask questions.
For more information contact:
