A food challenge test is a highly accurate method of determining the cause of a food allergy. The test uses capsules of various foods, some of which are suspected of causing an allergic reaction, which are taken like a pill by the patient. A period of observation after each dose allows a physician to monitor whether or not an allergic reaction takes place as a result of consuming that allergen.

Because a food challenge test involves provoking an allergic reaction, there is some risk associated with it. A food allergy reaction can be fatal if not immediately treated. The test should always take place at a site that is well-equipped to deal with any sort of reaction the individual may have. Food challenges should never be performed at home. Individuals who are susceptible to anaphylactic shock should participate in a food challenge test only if a physician determines that the test is absolutely necessary.

The test is performed without either the patient or the physician aware of which capsules contain the suspected problem foods. This eliminates the psychological effect of an expected response. If no allergic reaction takes place, the results suggest no allergy to that food type. This is then conclusively determined with an open challenge, which is the consumption of a regular portion of the food in question.

Before participating in a food challenge test, individuals will have to reduce the consumption of some medications, particularly antihistamines. Food should not be eaten several hours before the test takes place. A physician can offer specific guidance on what steps should be taken prior to the challenge.

Individuals who test positive for a food allergy will often retake the test to be sure the results are correct. If the results are substantiated with three positive test results, then complete removal of that food type from the diet is needed. A conclusive negative test result means that the food may be safely reintroduced to the diet.

Although highly accurate, food challenge tests can be time-consuming and expensive to perform, especially when multiple foods are being tested. For this reason, the test is usually performed to rule out a food allergy, so the physician can direct efforts at uncovering the true cause of a reaction.