This article discusses the purpose of oral food challenges, their risks, and what to expect before, during, and after the test.
Purpose of Test
OFCs are used to definitively diagnose a food allergy when there is a suspected allergy to a specific food. They are usually performed when other tests for food allergies, such as skin prick tests and blood tests, come back inconclusive. An OFC is also used to test whether a person has outgrown a known food allergy.
OFCs are different from oral immunotherapy (OIT). OIT is medical feeding therapy in which a person with a food allergy eats a very small amount of a specific food protein on a daily basis and slowly increases the dose over time. Its aim is to desensitize the immune system to no longer have an allergic reaction.
OFCs are very accurate in diagnosing food allergies.
Risks and Contraindications
The main risk of an OFC is an allergic reaction. In most cases, reactions are mild. Severe reactions are uncommon.
Most reactions to OFCs are skin (rash, hives), respiratory (nasal congestion, cough, difficulty breathing), or gastrointestinal (itchy mouth, stomach pain, vomiting, diarrhea) related. In severe cases, life-threatening anaphylaxis may occur.
To reduce the risk of a severe allergic reaction, doses start small and are then increased as no reaction occurs. Specially trained nurses and allergists (physicians who specialize in allergic conditions) are close by, with appropriate medications on hand if a reaction were to happen.
Risk factors that increase the chances of developing an allergic reaction during an OFC include:
Having asthma Age (the risk increases with increasing age) Type of allergen (especially peanuts, nuts, and seeds) Type of allergenic molecule Underlying immune-mediated reactions
Other factors that can contribute to a reaction during an OFC include:
Physical exercise Fever Severe infections Premenstrual syndrome Emotional stress Nonsteroidal anti-inflammatory drugs (NSAIDs) Alcohol consumption
Before the Test
When your healthcare provider refers you for an OFC, they may give you specific instructions on how to prepare for it. Each provider is different. However, some commonalities exist for what to expect in getting an OFC.
Timing
Due to the nature of an OFC, you should plan to be in the clinic for several hours as you’ll have to wait a specified amount of time after ingesting each dose. Oral food challenges can take anywhere from three to six hours or more.
Location
OFCs are typically performed at an allergy clinic, under medical supervision. This is because of the risk of an allergic reaction if one were to occur, and it ensures an accurate diagnosis.
Depending on the clinic, you will likely have a separate space or room to stay in during your appointment. Healthcare providers, including a nurse and an allergist, will be nearby for close supervision.
What to Wear
Wear comfortable clothing, as you will likely be in the clinic a long time. Bring an extra pair of clothing for you and your child (if your child is the one being tested), just in case any vomiting or other accidents occur.
Food and Drink
Check with your allergy clinic about whether you should abstain from food the morning of your appointment. Some clinics will ask you to fast, while others will allow you to have a small meal beforehand. Follow the instructions your healthcare provider has given you.
Typically, no food other than the food being tested is allowed to be eaten during the OFC. You might be permitted to bring a water bottle to sip from throughout the test. After the test is complete, you should be able to immediately consume a safe food after your appointment.
Health Insurance
Most health insurance policies cover oral food challenges. However, many require documentation of the appointment and may ask for your medical records. Some insurance providers require preapproval with documentation from your allergy specialist before covering any costs.
What to Bring
Because you will be waiting in the clinic for several hours, you should bring things to help pass the time. Books, toys, paper and pencil, or electronic devices can give you or your child something to do while waiting.
If your child is undergoing the OFC, they may wish to bring a comfort item, such as a favorite doll, stuffed animal, or blanket.
The clinic may require you to bring the food being challenged. If so, follow their instructions on preparing it and the serving size(s) you need to bring. Additionally, you will most likely be hungry after being in the clinic for hours, so you may wish to bring a safe food to eat after your appointment.
Make sure to have an epinephrine auto-injector (EpiPen) with you for the ride home, just in case of a delayed allergic reaction. Your clinic might also provide you with a list of what to bring. Review the list they give you before your appointment.
Other Considerations
Unless you (or your child) are having any asthma or allergy symptoms, do not take any quick-relief asthma medication or antihistamines three to five days prior to the test. These may interfere with the OFC and mask a reaction. Talk with your healthcare provider about any medications you are taking to see if they might interfere with the test.
If your child is being tested, do your best to explain to them what will be happening and relieve any anxiety they may be having about it. Allow them to ask any questions or bring up any concerns they may have. Then, address each one of them with simple and approachable terms.
During the Test
This section details what you should expect during your OFC at the allergy clinic. Each healthcare provider is unique, and their testing process and protocol may be slightly different. Follow the directions provided to you by your healthcare team.
Pre-Test
Before heading to the clinic, make sure you or your child being tested is healthy and has been so for at least 24 hours. You cannot have any cold symptoms, fever, or diarrhea. Any other medical conditions, such as asthma or eczema must be well managed and under control.
When you arrive at the clinic, you will get checked in and assigned a space or room where you’ll be for the next several hours. The nurses will prepare you or your child for the test and answer any questions you might have. The nurse will perform a physical exam and take vital signs before starting.
You may be required to sign a consent form explaining that an allergic reaction may occur during the appointment, along with possible treatment options.
Throughout the Test
The test will start by the nurse providing you or your child with a very small measured amount of the suspected food allergen. They will observe you closely for about 15 to 30 minutes.
If no symptoms occur, then they will give you another dose of the food that is just a little larger than the previous dose. A physical examination and vital signs might be performed by the nurse periodically throughout the OFC.
If you continue to have no reaction, this process will be repeated over the course of about one to three hours, with increasing dose amounts. Most OFC protocols recommend about four to six gradually increasing doses.
Post-Test
If you have successfully completed the OFC with no allergic reactions, you will be able to leave the clinic and return home. Usually, you will be advised to continue to watch for any delayed allergic reaction.
If a reaction does occur at the clinic during the OFC, your healthcare provider or nurse will be prepared to provide the appropriate care. This might be stopping the test and continuing observation, or it may mean administering medication. Severe allergic reactions may require intravenous (IV) hydration or other IV medications.
If the test is not conclusive or is stopped before the final dose of food is given, you may be asked to come back another day to repeat the OFC.
After the Test
After your appointment, you should be able to eat any safe food as desired. If no reaction occurred, the challenge food may be eaten on a regular basis at home beginning the day after the OFC.
If a reaction did happen, then a diagnosis of the food allergy would likely be made by your allergist and you should avoid that allergen or foods made with it indefinitely.
Interpreting Results
Results of the OFC are seen during the appointment, depending on whether an allergic reaction occurred or not. A negative test means no allergic reaction occurred, and you do not have an allergy to the suspected allergen.
Challenges that end in an allergic (positive) reaction establish an official allergy to the food and support the need to continue avoiding it.
Instead of considering it a negative, take an allergic reaction and diagnosis as a learning opportunity to know what a possible reaction can feel like and how you should respond if a future reaction were to occur.
Follow-Up
If your OFC was negative (no reaction), then you typically no longer need to meet with the allergist. It is normally recommended to make the now safe food a regular part of your diet.
If your OFC was positive (an allergic reaction occurred), you will need to continue to work with your allergist as advised. Your allergist can provide a treatment plan, write a prescription for any medications that may be needed, and provide instructions on what to do if another reaction were to happen.
If in the future you or your healthcare provider suspect that you or your child have outgrown the allergy, they might have you return to the clinic for another OFC.
Summary
An oral food challenge (OFC) is a test used to accurately diagnose food allergies. They are typically performed in an allergy clinic under medical supervision.
During an OFC, the suspected allergen is eaten in small doses that increase in size over time. If a reaction occurs, a food allergy is confirmed. If a reaction does not occur, then you are considered not to have an allergy to that specific food.
A Word From Verywell
Undergoing an oral food challenge can provoke anxiety. Prepare yourself or your child for the test by learning about the procedure and what to expect. Take comfort in knowing that if a reaction were to occur, your specialized healthcare team would be able to promptly and effectively manage it.
Remember that no matter the outcome, it is better to know for sure whether you have a true food allergy than to be uncertain. If desired, take a trusted family member or friend to accompany you to your OFC for support.
Open: Both the person being tested and the healthcare provider know what food is being eaten. Single blind: Only the healthcare provider knows whether the food or a placebo (an inert or harmless substance) is being eaten. Double blind: Neither the person being tested nor the healthcare provider knows whether the food or a placebo is being eaten.
Most OFCs performed at allergy clinics are open OFCs.
