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Challenge tests
Oral food challenges and drug challenge tests: understand why and how they are performed
In this sheet
The essentials in 30 seconds
The medical team decides whether to perform the test
It is not automatically performed for every patient and depends on your history, investigations and level of risk.
Never repeat the trial at home
A suspected food or medicine must not be tried again ‘to check’ without medical instructions.
Your condition must be sufficiently stable
Fever, infection, worsening asthma, a new reaction or a new treatment may lead the team to adapt or postpone the test.
Exposure is gradual and supervised
The food or medicine is administered according to a protocol selected for your situation. At each stage, the team decides whether to continue, wait or stop.
A reaction may occur
This is precisely why the test takes place in a setting with monitoring and the necessary treatments.
A negative result can be very good news
It may allow a food to be reintroduced or an unconfirmed drug-allergy label to be removed.
What is a challenge test?
A challenge test involves deliberately exposing a person, in a controlled and supervised way, to the substance being assessed. The aim is not to cause a reaction at all costs, but to obtain reliable diagnostic information when it is useful for care.
Why may this test be offered?
- confirm or rule out an allergy when the history and other tests are insufficient;
- check whether a food allergy has resolved over time;
- allow reintroduction of a food that is being avoided unnecessarily;
- check whether a suspected medicine can be used again;
- in some situations, identify a tolerated alternative medicine;
- avoid retaining an allergy label that unnecessarily limits treatment choices.
Oral food challenge
What is it used for?
An oral food challenge (OFC) involves gradually eating a food under medical supervision. It is the reference investigation when a food-allergy diagnosis remains uncertain or when checking whether tolerance has developed.
How should I prepare for my OFC?
- Read the instructions from the department carefully: they take priority over any general rule.
- Follow only the fasting or dietary instructions you have been given.
- Do not decide by yourself to stop an antihistamine or another treatment.
- Tell the department if you are unwell or have a fever, if your asthma has worsened or if your atopic dermatitis, urticaria or rhinitis is very active.
- Report any new medicine or reaction since the appointment was booked.
- Bring the food only if the department has asked you to, and in the requested form: brand, recipe, quantity, raw/cooked or another preparation.
What happens during an OFC?
Checks before starting
The team checks your health, treatments, initial reaction and whether instructions were followed.
First amount
A small amount of the food is given according to the selected protocol.
Gradual increase
Further amounts are offered at regular intervals if your clinical condition allows.
Observation
The team looks for symptoms and may decide to continue, wait or stop.
Monitoring after the final amount
An observation period continues even when there is no immediate reaction.
Conclusion
The team explains what the result means and what should happen next.
Negative OFC: what does the result mean?
A negative OFC means that the food was tolerated under the test conditions and up to the amount administered. The team then tells you how to reintroduce it into everyday life.
Positive OFC: what happens?
If symptoms meeting the medical criteria appear, the team stops or adapts the test and treats the reaction if necessary. The result is then explained and documented.
- A positive OFC is not a fault or poor performance.
- The test helps identify which foods genuinely need to be avoided.
- It may lead to changes in the emergency plan or care advice.
Drug challenge
What is it used for?
A drug challenge involves administering a suspected medicine, or an alternative depending on the clinical question, under supervision. It may confirm hypersensitivity, demonstrate that a medicine is tolerated or remove an unconfirmed allergy label.
Why does assessment differ between patients?
The strategy depends on the estimated risk based on the initial reaction, medicine, onset time, treatments received and any investigations already performed.
- in some low-risk situations, a direct challenge may be offered;
- in other situations, skin or laboratory tests may be useful first;
- for some severe reactions, re-exposure to the suspected medicine may be inappropriate or contraindicated.
Not every drug-reaction history should be rechallenged
Some severe drug eruptions or organ involvement generally make re-exposure to the suspected medicine dangerous. Examples include DRESS and Stevens–Johnson syndrome / toxic epidermal necrolysis. The decision belongs to a specialist team.
How should I prepare for a drug challenge?
- Bring the exact name of the suspected medicine and, if possible, a photograph of the box or an old prescription.
- Record the indication, dose if known, time between taking it and symptoms, and duration of the reaction.
- List the other medicines taken on the same day.
- Bring photographs, emergency or hospital reports and specialist letters if available.
- Tell the department if your health has changed, including infection, poorly controlled asthma, possible pregnancy, a new treatment or a new reaction.
- Never take the medicine again at home before the test ‘to check’.
What happens during a drug challenge?
The protocol is selected according to the medicine, initial reaction and level of risk. The medicine may be given in one or more stages, with observation periods between administrations and after the final dose.
What does a negative drug challenge mean?
It means that the medicine was tolerated under the conditions of the challenge. This may allow an allergy label to be removed or changed, according to the allergist’s conclusion.
- ask which exact medicine was tested;
- ask whether you can now receive it normally;
- check whether your medical record, allergy card or documents need updating;
- ask whether delayed reactions still need to be monitored after returning home.
What happens if I react during the test?
- administration is stopped or adapted according to the protocol;
- the team assesses the symptoms;
- treatment is provided if needed;
- monitoring continues;
- the result and its consequences are explained before you leave.
Challenge ≠ desensitisation
Challenge test
Main aim: determine whether the food or medicine causes a reaction or can be tolerated under the assessment conditions.
Desensitisation
A different therapeutic process used in some situations to allow administration of a substance despite a known allergy. It follows a specific protocol and must not be confused with a diagnostic test.
| Challenge test | Main aim: determine whether the food or medicine causes a reaction or can be tolerated under the assessment conditions. |
|---|---|
| Desensitisation | A different therapeutic process used in some situations to allow administration of a substance despite a known allergy. It follows a specific protocol and must not be confused with a diagnostic test. |
Before leaving the department
- I know whether the test is considered positive, negative or inconclusive.
- I know what I can eat or which medicine I can receive next.
- I know which precautions, if any, are still needed.
- I know whether my emergency plan, allergy card, medical record or prescriptions need changing.
- I know which possible delayed symptoms should prompt me to contact the department or seek advice.
Common misconceptions
‘I can test a very small amount at home.’
No. If a challenge is needed, it must be performed in the setting defined by the medical team.
‘My skin prick tests are positive, so the OFC is pointless.’
Not necessarily. A positive test shows sensitisation; an OFC may be needed when actual tolerance remains uncertain.
‘If the OFC is positive, I failed the test.’
No. A reaction provides clinical information that guides care.
‘A drug-allergy label is always permanent.’
No. Some labels can be reassessed, but only with a strategy suited to the risk.
‘Challenge and desensitisation are the same thing.’
No. One is mainly diagnostic; the other is a specific therapeutic process.
| ‘I can test a very small amount at home.’ | No. If a challenge is needed, it must be performed in the setting defined by the medical team. |
|---|---|
| ‘My skin prick tests are positive, so the OFC is pointless.’ | Not necessarily. A positive test shows sensitisation; an OFC may be needed when actual tolerance remains uncertain. |
| ‘If the OFC is positive, I failed the test.’ | No. A reaction provides clinical information that guides care. |
| ‘A drug-allergy label is always permanent.’ | No. Some labels can be reassessed, but only with a strategy suited to the risk. |
| ‘Challenge and desensitisation are the same thing.’ | No. One is mainly diagnostic; the other is a specific therapeutic process. |
Key points
- A challenge test is a controlled exposure decided by a medical team.
- Never take a suspected food or medicine again at home solely ‘to check’.
- Skin prick tests and specific IgE are useful but do not always answer whether something is actually tolerated.
- An OFC or drug challenge can confirm an allergy, but may also remove avoidance or an incorrect label.
- Protocols are personalised: there is no universal dose, fasting period or medicine-withdrawal interval for every patient.
- Before leaving, you should understand what the result changes for you in practice.
Prepare for and describe the reaction
You may also want to read
Main references
- Sampson HA, Arasi S, Bahnson HT, et al. AAAAI-EAACI PRACTALL: Standardizing oral food challenges - 2024 Update. Pediatr Allergy Immunol. 2024;35(11):e14276. doi:10.1111/pai.14276. PMID: 39560049.
- Santos AF, Riggioni C, Agache I, et al. EAACI guidelines on the diagnosis of IgE-mediated food allergy. Allergy. 2023;78(12):3057-3076. doi:10.1111/all.15902. PMID: 37815205.
- Barbaud A, Heise Garvey L, Torres M, et al. EAACI/ENDA position paper on drug provocation testing. Allergy. 2024;79(3):565-579. doi:10.1111/all.15996. PMID: 38155501.
- Assurance Maladie. Allergie alimentaire : consultation médicale et mesures au quotidien. Ressource patient consultée pour le TPO et le suivi de la tolérance.
This sheet provides general guidance. It does not replace instructions from the department performing your test, your prescription, your emergency plan or decisions made by the medical team.
SOS Allergo — Information for patients and caregivers. This sheet does not replace a medical consultation or personalised instructions from your healthcare professional.
Scientific review: September 2026 · sosallergo.fr