Now that Mitch is two years old, our allergist agreed that it was time for additional food allergy testing to find out if Mitch has outgrown any of his current allergies or if he has any new food allergies to suspect foods. Our last few attempts at retesting Mitch via an IgE RAST test has been anything but successful. Mitch has rolling veins that no phlebotomist can get, and attempt to find his veins is not only torturous for him but for us as parents as well. After talking to his allergist about our situation, we decided to try a round of skin prick (scratch) tests and compare the results to his earlier IgE RAST tests.
We tested Mitch for 26 different allergens including 19 allergens he had previously tested positive for, and a few new suspected allergens we found. Though this food allergy testing can be uncomfortable, little Mitch was a champ lying quietly while playing Angry Birds. (Thank goodness for iPhones! How did our parents ever do things without all these gadgets to keep kids busy?) Around 15-20 minutes later we had our results, and Mitch was cleaned up and slathered in Benadryl.
We couldn’t believe the test results! Eight of the nineteen allergens Mitch previously tested positive for did not produce a wheal, and another six allergens produced a wheal that was 3mm or less, a size that is commonly counted as a negative reaction. Three more allergens had a wheal of 4-5mm. We were blown away after we were given the OK to do home oral food challenges with all of Mitch’s allergens except for peanuts (11mm wheal), tree nuts (0-20mm wheal) and barley (7mm wheal).
Could Mitch really be outgrowing some of his food allergies?
Food Allergy Testing – Skin Prick Test
If you’re unfamiliar with skin prick (scratch) food allergy testing, a microscopic amount of an allergen is introduced to a patient’s skin by various means including a prick test or scratch test (the pricking the skin with a needle or pin containing a small amount of the allergen) or a patch test (by applying a patch to the skin, where the patch contains the allergen).
If an immuno-response is seen in the form of a rash, urticaria (hives), or (worse) anaphylaxis it can be concluded that the patient has a hypersensitivity (or allergy) to that allergen. Further testing can be done to identify the particular allergen.
Some allergies are identified in a few minutes but others may take several days. In all cases where the test is positive, the skin will become raised, red and appear itchy. The results are recorded- larger wheals indicating that the subject is more sensitive to that particular allergen. A negative test does not mean that the subject is not allergic; simply that either the right concentration was not used or the body failed to elicit a response.