What Is an Oral Food Challenge?

Reviewed by: HU Medical Review Board | Last reviewed: March 2022

Do you think you have a food allergy or intolerance? Maybe you wonder if a confirmed food allergy has gone away. If so, an oral food challenge (OFC) may provide answers.

A food challenge is a test used to diagnose food allergies. This test can detect a food allergy from food intolerance. An OFC has 3 steps:1-3

  • Food removal
  • Food test
  • Watching

How is an oral food challenge given?

An OFC test starts with an elimination diet. This means you stop eating certain foods for a time. This time ranges from 2 to 4 weeks.2

The next stage is done in your doctor’s office. During this stage, your doctor gives you doses of the foods to which you may be allergic. The doses start small and increase little by little. There is some time between doses to see if you react. You consume each dose in front of your doctor on 1 or more days.1-3

Watching is the most telling step. Your doctor watches to see if you have a reaction for 1 to 6 hours after you eat the food. They may end the OFC at any time during this test if serious allergic reactions appear. If you do have a reaction, your doctor will treat your symptoms.1-3

The results of the food challenge will support either avoiding certain foods or adding them back to your diet. An allergic response to a test food confirms a food allergy and the need for avoidance. If no symptoms appear, you are not allergic and may be able to eat that food.1-3

Types of oral food challenge tests

There are 3 types of OFCs:1-3

  • Open food challenge
  • Double-blind, placebo-controlled food challenge
  • Single-blind food challenge

An open food challenge is the most common challenge test done in doctor’s offices.

When conducting research, the double-blind challenge is the gold standard. This test means you and your doctor cannot tell which dose contains the food to which you may be allergic. In a single-blind food challenge, only the doctor knows when you receive a test food. Blinded tests help eliminate any food biases that may sway the outcome.1-3

When is an oral food challenge given?

Your doctor may give a food challenge if you have symptoms of a food allergy but your skin and blood tests did not reveal an allergy. A food challenge may also be helpful to verify a food allergy if test results are unclear. In some cases, the OFC may point to a food intolerance.1-4

Doctors use OFCs to help develop a treatment plan. Avoidance is the standard treatment for a food allergy. But with intolerance, eating the food on a routine basis may help your body better tolerate it. In some cases, avoiding less tolerable foods can lead to food allergies.4

Doctors may use an OFC to check if an allergy has gone away. Perhaps avoiding certain foods has become harder for you or you need more nutrients. Sometimes, your body will no longer react to a food after a certain amount of time.1-3

How to prepare for an oral food challenge

If you and your doctor decide to do an OFC, you need to prepare. Your doctor will give you specific instructions, but they will likely include:2,3

  • Avoid certain foods or drugs in the days or weeks ahead of the challenge
  • Do not eat or drink anything other than water for 2 to 4 hours before the OFC
  • Bring any epinephrine auto-injectors you have with you to the test site

You should also prepare to be in the office for several hours for the food challenge.2,3

The doctor running the food challenge must prepare the test foods and the test site. They may need to mix test foods with other foods and measure the doses. They will also gather any drugs and supplies needed to treat allergic responses.2,3

Who should not have an OFC?

A food challenge is not right for everyone. These include when people are pregnant, sick, or taking certain medicines. Also, a doctor would not give an OFC for a food you do not eat because the test would be a waste of time and money.2,3

If your risk for a severe allergic reaction is high, your doctor may not order an OFC. The risk is greater if your blood and skin tests reveal an allergy, or if you have had a current or intense allergic response. Certain health problems like anxiety also raise the risk.2,3

Is an oral food challenge safe?

An OFC is safe when done according to medical standards. The test must take place in a doctor’s office or hospital. A doctor must watch you during the challenge.1-3

You may have an allergic response to a test food. Common symptoms include flushing and hives. The doctor may give you antihistamines for these reactions. A severe reaction like anaphylaxis may occur but is less likely. In this case, they would use epinephrine.1-3

An OFC may bring good news. You may not have a food allergy. If you can handle eating certain foods, you no longer need to avoid them.

Adding more foods to your diet can enhance your life. The extra food can increase your nutrition and overall health. Knowing you do not have to pass up foods can reduce stress and make eating more pleasant.

If the test confirms a food allergy, you will know for sure that you need to avoid that food. Or, you may learn how much of the food will cause a reaction for you.

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