Auckland DHB Clinical Immunology and Allergy
Public Service, Allergy and Immunology
A food challenge is a definitive way of testing for the presence of a food allergy. Usually an allergist begins the process of diagnosing a food allergy with a detailed history about previous exposure to the food(s) in question and symptoms that arose following intake of the food. Often allergy testing with blood and/or skin testing will follow. However sometimes, even with this information, it still isn’t clear whether there is an allergy to a particular food or not.
In these circumstances, a food challenge can offer valuable information about the way in which the body will respond to intake of the food in question. It can therefore be a very accurate diagnostic test.
A food challenge involves being given carefully measured amounts of a food to eat under monitoring. Usually this is done in a specialised environment with highly trained medical professionals. Schedules have been developed for the optimal amounts to use, and time intervals between doses in order to optimise safety. The initial amounts of food are very small and unlikely to cause a significant allergic response, even in an individual with allergy. If signs of an allergic reaction are displayed during a food challenge, this is treated accordingly. Often food challenges are conducted ‘blinded’. This means that either the patient alone, or both the patient and health professional are unaware of whether any given dose contains the food being tested or not. This increases the objectivity of the test. This is because biases or preconceived notions about allergy (of either patient or doctor) are removed.
At the end of a food challenge, it is often known whether
a) there isn’t an allergy to the tested food (therefore it is safe to eat it)
b) there is a food allergy (therefore the food should be avoided).
However, like any diagnostic test, sometimes there isn’t a clear result, and the challenge may need to be repeated or another step taken.