An elimination diet is used to detect foods that might be the cause of allergies and consists of fasting or consuming foods which have a low allergic rate (such as rice, lamb, cabbage) for 4-7 days until symptoms clear. If symptoms disappear during this period, commonly consumed foods are then reintroduced one at a time in the hope of finding the culprit. Some consider it important to be on an elimination diet longer than a week. This is because it may take up to 3 weeks for chronic symptoms to disappear as the body reverts from a state of allergy-addiction (corresponding to Selye's adaptation stage) to one of increased alertness and sensitivity (corresponding to Selye's alarm stage). In this hypersensitive state, ingestion of an offending food results in a rapid and exaggerated reaction, allowing the patient to identify previously unsuspected allergens.

An elimination diet can be accurate, but difficult at the same time. Most food allergy symptoms do not appear soon enough after consuming the food to easily make the connection. However, after avoiding the food for some time, as in an elimination diet, reintroduction of the offending food results in a more rapid and pronounced symptom onset. This makes it easier to identify which food is causing the problem.