4. Oral Challenge Test
After a skin-prick, intradermal, and/or blood test determines that the possibility of a reaction to a food is unlikely, patients may be given an oral “challenge test”. For this test, they are given a tiny amount of the substance to eat, and if they don’t react, they are given increasingly larger amounts over several hours.
If the patient reacts, the test is stopped and the reaction is treated. If the patient doesn’t react, he or she can be assured that the food is safe to eat.
Challenge tests usually happen in the allergist’s office, but when there is a risk of a potentially serious reaction, they may be performed in a hospital. Some allergists will not perform this test at all when the risk is considered high.
While the risk of challenge tests is greater than the risk associate with the skin-prick, intradermal, and blood tests, they are considered the only truly accurate measure of a food allergy, and can help patients who are unnecessarily avoiding certain foods.
However, if you pass the challenge, it doesn’t always mean you’re not allergic, because some patients can react again after a period of time or under different circumstances. For example, a patient who is pollen-allergic may react to a food during pollen season, but not in winter.
List of Food Allergy Tests to Avoid
The National Institute of Allergy and Infectious Diseases (NIAID) says in its food allergy guidelines for physicians that the following tests are not recognized or recommended. According to the expert panel who developed the guidelines, these tests are “non-standardized and unproven procedures” for evaluating true (IgE-mediated) food allergy:
- Basophil histamine release/activation
- Lymphocyte stimulation
- Facial thermography
- Gastric juice analysis
- Endoscopic allergen provocation
- Hair analysis
- Applied kinesiology
- Provocation neutralization
- Allergen-specific IgG4
- Cytotoxicity assays
- Electrodermal test (Vega)
- Mediator release assay (LEAP diet)