What is an oral food challenge?
An oral food challenge is a type of allergy test. It is the best test to diagnose a food allergy.
An oral food challenge is used for people with immediate type allergy (IgE mediated). IgE mediated allergy is the type of allergy which can cause anaphylaxis.
Oral food challenges may also be used for people with a delayed non-IgE mediated allergy called Food Protein-Induced Enterocolitis Syndrome (FPIES).
When might I be offered an oral food challenge?
An oral food challenge may be recommended by an allergy specialist to help confirm a diagnosis or better understand a person’s food allergy. This test may be offered when:
- It is unclear whether a food is causing allergic reactions
- There is a need to check if a previously diagnosed food allergy is still present
- It is possible that a food can be safely eaten in a baked form, even if it cannot be tolerated raw or lightly cooked (this is common with egg and milk)
- A person has a positive skin prick or blood test to a food they have never eaten, and it is necessary to confirm whether a true allergy exists
- A person is about to start an oral immunotherapy (OIT) treatment program
- When a person is involved in a research study
What does an oral food challenge involve?
An oral food challenge is usually ordered by an allergy specialist and is often done by a nurse who works with them. Oral food challenges should be done in a clinical setting such as a public hospital, private hospital or private specialist rooms so that medical help and equipment is close by if needed.
The food is eaten in small and increasing amounts over a few hours. The person then stays for at least 1 or 2 hours afterwards (sometimes longer) to watch for any allergic reaction.
The Australasian Society of Clinical Immunology and Allergy (ASCIA) has protocols (a guide for health professionals) on how the oral food challenge should be done. Research studies may have their own protocols.
Preparing for your oral food challenge
The clinic should provide you with instructions before your oral food challenge. This may include:
Avoid antihistamine before your appointment if possible
You should be told how long you will need to avoid taking antihistamine before an oral food challenge (for example Zyrtec®, Telfast®, Claratyne®). Taking antihistamines before an oral food challenge may make it harder to recognise if you are having a reaction. You may also need to have a skin prick test if you have not had one recently and antihistamines can affect the accuracy of the skin prick test. Check with the clinic if you are unsure.
If you are unwell or have an allergic reaction in the days before your oral food challenge:
Contact the clinic doing your oral food challenge and tell them you or your child is unwell. This includes cough, cold, fever, gastroenteritis.
If you have an allergic reaction in the days before your oral food challenge, please follow your ASCIA Action Plan. Your safety is the priority; the oral food challenge can always be rescheduled.
Tell clinic staff if you have experienced an allergic reaction that required antihistamines or adrenaline, or if you have taken your asthma medication for an asthma flare.
In the case of sickness or use of medications, the oral food challenge may need to be rescheduled. Check with the clinic if you are unsure.
What should I take to an oral food challenge?
An oral food challenge can take about 4-6 hours, more if there is an allergic reaction. You should be told what to bring by the clinic, but here is a list of things which may be helpful:
Food that is being challenged. You will usually be told if you need to bring the food and in what form. For example,
- If a young child is having an oral food challenge to almond, almond meal (flour), paste or crushed nuts are used instead of whole almonds or pieces. If the oral food challenge is for fish, you may be asked to bring different types of fish (such as flathead or salmon). You may be asked to cook the fish at home and bring in some raw fish as this might be used for skin prick testing
- You should be given a recipe or told what brand of biscuits to bring with you if your oral food challenge is to see if you can tolerate egg or milk in baked form
Food that you/your child eats regularly to mix with the challenge food to make it more enjoyable to eat. For example:
- yoghurt, ice cream or fruit/vegetable puree
- tomato sauce, rice or pasta
- Food that you eat regularly – especially if you have a long way to travel home afterwards
- Something to do- books, electronic devices, homework, toys for young children
- Phone/electronic device charger
- A change of clothes for you and your child. Useful if something spills or someone vomits
- Medicare card
- Your usual allergy emergency medications and ASCIA Action Plan, including adrenaline device
What happens at an oral food challenge?
Your doctor will discuss why they think you should do an oral food challenge and what the benefits and risks are. If you agree to do the oral food challenge, the doctor will order it. Sometimes you have to wait a long time for your oral food challenge appointment.
Consent
You often need to sign a consent form before doing an oral food challenge. This may be done when the oral food challenge is ordered by the doctor or on the day it is done.
Assessment
A nurse or doctor will check you before you are given the food. They may ask you questions, look at your skin, listen to your breathing, measure your heart rate, blood pressure and oxygen saturations.
This helps the nurse or doctor decide if you are well enough to have the oral food challenge and to see if there are any changes during the oral food challenge.
Sometimes you may need to have a skin prick test before the oral food challenge.
Overview
- Before you start
A nurse or doctor will check that you are well and ready to begin.
- First “dose” of food
You will eat a very small amount of the food.
- Wait and watch
You will wait about 15–30 minutes (sometimes longer) while the team checks how you are feeling.
- Gradually increasing amounts
If you are feeling well, you will have more of the food.
This is repeated every 15–20 minutes, with the amount of food slowly increasing.
Most challenges involve 4–6 doses in total.
- Monitoring throughout
After each dose, the nurse or doctor will ask how you are feeling and check for any symptoms.
Important:
Tell the nurse or doctor straight away if you feel unwell or notice any symptoms (such as itching, rash, stomach pain, or trouble breathing) at any time during or after the challenge. They are there to keep you safe and can treat any reactions if needed.
It is ok to feel nervous when having an oral food challenge, many people do. Talk with your health professional about the risks and benefits of an oral food challenge and ask questions.
There are often long wait lists for oral food challenges so it is important to let staff know if you cannot make it to your appointment so they can offer it to someone else.
What if I have an allergic reaction to the food during the oral food challenge?
Most people will not have an allergic reaction when having an oral food challenge. However, they can still happen. This is why an oral food challenge is always done where medical help is available.
If you have an allergic reaction during an oral food challenge, you will be treated and observed by medical and nursing staff.
If your reaction is anaphylaxis, you will be given adrenaline. If the challenge is not being done in a hospital you should be taken to hospital by ambulance, as stated on the ASCIA Action Plan for Anaphylaxis.
After anaphylaxis you should be observed for the recommended 4 hours and on rare occasions may have to stay in hospital overnight.
Results of an oral food challenge
If a person reacts to the food during an oral food challenge, then the challenge result is said to be positive. This means that the person is allergic to that food, and they should avoid eating it.
If a person does not react to the food during the oral food challenge, the result is negative. This means the person is not allergic to that food and they should keep eating it on a regular basis.
On rare occasions the result is unclear. Your doctor will talk to you about whether the oral food challenge should be done again on another day.
What are the risks of an oral food challenge?
The main risk is an allergic reaction including anaphylaxis.
What are the benefits of an oral food challenge?
Negative oral food challenge
(able to eat the food without symptoms)
- Improved nutrition as able to eat more foods
- Social advantages of an expanded diet and no longer being allergic (unless the person is still allergic to other foods)
Positive oral food challenge
(the food triggered a reaction)
- Confirming the person is still allergic to the food and knowing it must be avoided
- Experiencing how well adrenaline works to treat anaphylaxis. This helps people understand the importance of carrying their adrenaline device and using it if having anaphylaxis
Do I have to keep eating the food after a negative oral food challenge?
Keeping the food in the diet is important. An oral food challenge should not be done if the person with the allergy or their parent/carer do not plan to keep the food regularly in the diet. If the food is not eaten regularly, the food allergy is more likely to return.
The usual advice is to eat the food at least once a week, but your health professional will advise you.
For many people it can be difficult to keep the food in the diet. They may not be used to the texture, smell or taste. Talk with your health professional (doctor, nurse, dietitian) about ways to keep the food in the diet.
Useful links
ASCIA has further information on Food Allergen Challenges.
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