Food Challenge Test

What is a food challenge test?

An oral food challenge test is a highly reliable test that determines if a person has a food allergy. Food challenges can also tell you if you’ve outgrown a food allergy or if you need to continue to avoid a food due to an allergy. The test involves eating increasing amounts of a suspected allergen under the supervision of your healthcare provider. You should never attempt a food challenge test at home.

Food challenge tests generally follow these steps:

• Your healthcare provider or allergist gives you the suspected allergen in small doses. Sometimes, the food is in a capsule you swallow.
• Your provider watches you closely to see if you have an allergic reaction.
• If no reaction occurs after about 15 minutes, they give you another small dose of the suspected allergen.
• They repeat these steps until either an allergic reaction occurs, or you’ve taken the full dose of the allergen (usually broken up into four to six doses).
• If you show signs of a reaction at any time, the test ends and your provider confirms you have an allergy.
• If no reaction occurs after you’ve had the entire dose, you aren’t allergic to that food.
• Only one food allergen is challenged at a time (in most cases).

Because you can experience a serious allergic reaction, your allergist performs an oral food challenge in a hospital or medical office. This ensures that the appropriate medical care is nearby should an emergency occur. There are standards that allergists follow to ensure the test goes as smoothly and safely as possible. It’s considered the “gold standard” for diagnosing food allergies.

When would I have an oral food challenge test?

Food challenge tests typically occur if a skin prick test and allergy blood test didn’t provide a definitive answer as to whether a person is allergic to a certain food. Skin prick tests and blood tests are still reliable and helpful to healthcare providers, but these allergy tests have a higher chance of giving inconclusive results.

Most people have food challenge tests to check for an IgE-mediated food allergy. IgE-mediated means that IgE allergy antibodies cause the allergic reaction. These types of allergies typically produce an immediate reaction to a food.

How is an oral food challenge test done?

There are different methods healthcare providers use to perform a food challenge test. All methods involve eating increasing amounts of a suspected allergen under medical supervision.

Samples of the suspected offending food are sometimes taken on their own, but other times, they’re mixed with something else. For example, if the allergen is peanut butter, you could have plain peanut butter or a cookie that contains peanut butter. Sometimes the food is disguised in a capsule that you swallow like a pill.

These food preparation techniques are sometimes used to prevent a person from recognizing the offending food by sight or smell. In some situations, your healthcare provider may ask you to bring your own food to the test. You may even be asked to cook a specific recipe containing the suspected offending food to bring in. After eating the food or taking the capsule, you’ll be monitored to see if a reaction occurs.

Someone with a history of severe reactions can’t participate in a food challenge test unless it’s being done to see if the person has outgrown the food allergy. In most cases, only one food can be challenged at a time.

Types of oral food challenges

There are three different types of food challenges. All food challenge tests take place in a hospital or healthcare provider’s office.

Double-blind, placebo-controlled

With this method, you and your allergist don’t know which capsule or food contains the suspected allergen or which is a placebo. The placebo is harmless and doesn’t contain the allergen. The allergen and placebo are given several hours or days apart.

The benefits of this test are that a person’s anxiety or the allergist’s preconceptions about the allergen can’t interfere with the test. It essentially removes outside factors that can sway the outcome. While it’s the ideal way to perform a food challenge test, it’s rare in clinical settings and mostly used in research studies.

Single-blind

In this test, only your allergist knows which food or capsule is the suspected allergen and which is the placebo. The allergen and placebo are given hours or days apart.

Open-food

In an open food challenge, you and your allergist know what allergen you’re receiving. Your allergist breaks up a single serving size portion of the allergen and has you take it in increasing amounts over approximately one hour. They monitor you the entire time for an allergic reaction. It’s the most common way to perform the test.

Do I need to prepare for a food challenge test?

Your healthcare provider may give you some instructions before the test to ensure your results are reliable. These instructions could include:

• Avoid any known allergens for up to two weeks before the test.
• Stop any prescription or over-the-counter (OTC) antihistamines before the test.
• Refrain from eating or drinking in the hours leading up to the test.

It’s important to talk to your provider about your allergies and what medications you take. You shouldn’t avoid taking medications like inhaled-asthma medications or epinephrine in an emergency because you have a food test scheduled. Your provider can talk to you about what to take and when to take it.

Your healthcare provider may also ask that you cancel the test if you have cold or flu-like symptoms on the morning of the test.

What can I expect during a food challenge test?

It’s OK to feel a little anxious about the test. Rest assured the test is safe and your healthcare provider is monitoring your vital signs for the duration of the test.

Your allergist will give you a small serving of the suspected allergen, then watch and wait for a reaction. If there are no symptoms of a reaction, they give you a second dose. Careful monitoring occurs after each dose.

If you show a reaction, the challenge is over. Your provider will give you medications to help with your allergy symptoms.

How long does the test take?

It can take up to three or four hours to complete the test, regardless of how you react. Most healthcare providers give you a small portion of the allergen in 15-minute increments. If you show an allergic reaction early in the test, the test ends. But your provider will keep you for monitoring for up to two hours. It can also last even longer depending on how you react. Even if you’ve eaten the entire dose of the allergen without a reaction, your provider may monitor you for up to two hours afterward.

What should I expect after the test?

If your allergist confirms you have an allergy, they’ll talk to you about ways to avoid the food and prescribe you any necessary medication, like epinephrine (EpiPen®). If you aren’t allergic to a food, you can begin eating that food as a part of your normal diet. Having a reaction after you’ve passed a food challenge is uncommon.

Is an oral food challenge safe?

There are risks to a food challenge test. That’s why the test takes place in your healthcare provider’s office under their supervision. Most people experience minor reactions to food allergens, like hives or skin irritation. Your allergist can give you medications to relieve these symptoms.

Severe reactions aren’t common, but if they should happen, your provider is ready to administer the care you need. Serious risks of an oral food challenge can include difficulty breathing or anaphylaxis.

Benefits of an oral food challenge

The benefits of a food challenge include being able to expand your food choices and knowing for certain if a food will trigger an allergic reaction. Knowing if you have an allergy can help you prevent a future allergic reaction from occurring.

What do the results of an oral food challenge test mean?

Results of an oral food challenge test are almost immediate. Healthcare providers typically classify the test results as either tolerated or reacted.

• A tolerated result means you had no allergic reaction to the food and the food should be safe to eat.
• A reacted result means there was an allergic reaction during testing.

It’s also possible to have an inconclusive result. Your allergist may recommend avoiding the food to be safe.

Are food sensitivity tests FDA-approved?

An at-home food sensitivity test isn’t the same as a food challenge test your healthcare provider performs. Most of the tests on the market aren’t approved by the Food & Drug Administration (FDA) and don’t have any clinical value. This means the tests you can buy online or at your local drugstore don’t replace a diagnosis by a healthcare provider.

A note from Cleveland Clinic

An oral food challenge test is considered the gold standard for diagnosing food allergies. While it may sound scary to think about purposely eating a food you think you’re allergic to, rest assured that your healthcare provider is with you for the whole test. Talk to your provider about your concerns and don’t be afraid to ask questions about what would happen in an emergency.