An oral food challenge is the definitive food allergy diagnostic test.
During an oral food challenge (OFC), patients swallow specific doses of foods suspected of causing allergic reactions. The food dose, initially very small, is gradually increased during the challenge. Patients are monitored to see whether allergic symptoms occur.
If there are no allergic symptoms during a food challenge, food allergy is ruled out as a diagnosis. If an OFC results in allergy symptoms, and the symptoms are consistent with the patient’s medical history and lab tests, a food allergy diagnosis is confirmed.
Three OFC Types
Unless healthcare consumers have researched OFCs, they may not realize there are three types. Most medical facilities likely offer the least expensive type, called an open food challenge, and much of the time this is sufficient for a diagnosis.
In an open food challenge, the patient and the healthcare professionals know that a suspected allergen is being ingested by the patient. No harmless substances, called placebos, are swallowed during the test.
Sometimes medical providers use a single-blind food challenge, which is the second best of the three OFC options. In this test, the treatment professional knows what the patient is ingesting (either suspected food or placebo) but the patient is not informed.
The third type of OFC, and considered the best option, is the double-blind* placebo-controlled food challenge. During this test, patients do not know if they are getting increased doses of a suspected food allergen, or a placebo—and neither does the medical professional.
The Proven Open Option
Though the double-blind placebo-controlled option is the more specific test for food allergy diagnosis, it is also inconvenient (for patient and professional) and the most expensive. At many facilities, double or single blind tests may not be offered. However, open food challenges are proven to provide most patients the food allergy answers they need.
Note: The open food challenge, and the single and double blind tests, each carries the risk of severe allergic response, including anaphylaxis. These tests should always be performed by trained professionals at a medical facility.
*Double-blind studies guard against placebo effects, and help prevent any test administrator bias or influence from affecting the test results. Placebo effects are outcomes owed to the patient’s thoughts or beliefs about a test or treatment.