There are several steps that should be taken before a food challenge test to prevent interferences that could affect the test results. It is important that individuals consult with a physician for specific preparation instructions, which generally include:

• In the seven- to 14-day period before the test, eliminate all foods that are suspected allergy triggers from the diet. This helps ensure that any allergic response that takes place during the test is caused by one of the test challenges, and not earlier allergen contact.
  
  
• Do not consume anything more than water in the two hours prior to the test (a physician may recommend a longer fasting period in some adults). It is best to administer the test to a person with an empty stomach. This further ensures that any allergic reactions experienced during the test were the direct result of a food challenge.
  
  
• Discontinue the use of antihistamines for three to seven days before the test and minimize the amount of other medications taken. A physician will be able to safely schedule these medication changes. Though many types of antihistamines and other medications are effective at blocking or reducing allergic reactions, this works against accurate test results. For the test, the individual needs to be as sensitive to the allergens as is safely possible.
  
  
• Individuals should not have taken a food challenge test for a different food type within three to five days of the test.

The food challenge test can be a lengthy procedure that requires the whole day. Though any sort of allergic reaction that occurs during the testing will be immediately treated in a clinical setting, it might be a good idea for patients to have someone available to drive them home in case symptoms persist.