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Adult & children's allergy services since 1982
Mon - Sat: 9am - 6pm
An oral food challenge is the most accurate and reliable way to diagnose or exclude a food allergy. Often described as the “gold standard” in allergy testing, it involves carefully introducing a suspected food allergen in gradually increasing quantities under close medical supervision.
At The London Allergy Clinic, oral food challenges are consultant-led and carried out in a fully equipped clinical environment at The Fitzrovia Hospital, ensuring the highest standards of patient safety and care.
Many patients have previously conducted allergy blood tests or skin prick tests, which are reliable and useful diagnostic tools, but only an oral food challenge can provide a definitive answer about whether an allergy exists; the nature of the reaction the patient willl have, and what quantity of food will trigger the reaction.
This can be particularly important for:
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Individuals undergoing medical assessments for the Armed Forces.
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Applicants to the British Army, Royal Navy or Royal Air Force.
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Patients seeking occupational clearance.
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Individuals wishing to clarify whether a childhood allergy has resolved.
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Patients with uncertain or conflicting allergy test results.
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Those who wish to understand whether they remain at risk of a severe allergic reaction.
In many cases, a successful oral food challenge can provide reassurance and formal clinical evidence that a food can be safely consumed.
How an Oral Food Challenge Works
Oral food challenges are performed under strict medical supervision by experienced allergy consultants and trained clinical staff.
The challenge involves carefully measured doses of the food being introduced in stages.
Typically, the process starts with a skin prick test and then moves onto the challenge which includes:
1. Initial contact stage
A tiny amount of the food may first be rubbed onto the lip to observe for any immediate local reaction.
2. Very small oral dose
A carefully measured quantity of the food is then eaten.
3. Observation period
The patient is closely monitored for approximately 15–20 minutes after each stage.
4. Gradually increasing doses
If no reaction occurs, progressively larger quantities of the food are administered at each step.
5. Final assessment
Once the full challenge is completed, the consultant will discuss the outcome and next steps.
Throughout the challenge, patients are continuously monitored for signs of an allergic reaction.
Monitoring includes:
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Blood pressure
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Oxygen saturation levels
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Peak flow measurements
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Clinical observation for rash, swelling, wheeze or other symptoms
Patients are also encouraged to report any symptoms that may not be externally visible, such as tingling, itching, throat discomfort or nausea.
Safety During Oral Food Challenges
Because oral food challenges intentionally involve exposure to a suspected allergen, they should only be performed in a medically supervised setting with immediate access to emergency treatment and resuscitation equipment.
At the London Allergy Clinic:
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All challenges are consultant-led
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Emergency medications and equipment are immediately available
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Challenges take place in a hospital environment
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Patients are monitored throughout the procedure and recovery period
Although reactions can occur during an oral food challenge, the purpose of the controlled environment is to ensure that any symptoms are recognised and treated promptly and appropriately.
Not all allergies are suitable for testing via an oral food challenge. If the allergy is suspected to be severe, it may not be safe to perform a challenge. This is a decision that will be made by the doctor after a careful assessment.
How long does an oral food challenge take?
Most oral food challenges take several hours to complete. The exact duration depends on:
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The food being tested
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The dosing schedule required
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The patient’s clinical history
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Whether any symptoms occur during the procedure
Patients should expect to remain in the hospital for most of the day.
Oral Food Challenges for Military and Occupational Clearance
We regularly see patients who require formal allergy assessment for occupational purposes.
Certain careers — particularly within the Armed Forces, aviation and emergency services — may require clarification regarding food allergy risk (BSACI medical assessments).
An oral food challenge can provide objective medical evidence regarding:
- Whether an allergy exists
- Whether an EpiPen (or other auto-injector) is required
- The likelihood of a severe reaction
Formal clinic letters are provided following assessment.
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