Oral Allergy Syndrome: Why Fresh Fruit Makes Your Mouth Itch

Published: 28 February 2026

You bite into a fresh apple and within seconds your lips start tingling, your tongue feels prickly, and the roof of your mouth itches. A few minutes later the sensation fades. You can eat apple crumble with no trouble at all — so what is going on?

The answer, for many people in the UK, is oral allergy syndrome (OAS), a common but widely misunderstood form of food-related allergic reaction. Also known as pollen food syndrome, it affects an estimated two per cent of the UK adult population — and the figure may be higher, because many people never seek assessment (Allergy UK, 2025). This guide explains why it happens, which foods and pollens are involved, how to tell OAS from a more significant food allergy, and when IgE blood testing can help clarify your sensitisation pattern.

What Oral Allergy Syndrome Is (and Why It Is Also Called Pollen-Food Syndrome)

Oral allergy syndrome is an IgE-mediated allergic reaction that typically causes rapid-onset symptoms confined to the mouth, lips, tongue, and throat after eating certain raw fruits, vegetables, or tree nuts. The term “pollen food syndrome” (PFS) is now preferred by many allergists because it more accurately describes what is happening: your immune system is reacting to food proteins that resemble the pollen proteins you are already sensitised to (BSACI, 2023).

Typical symptoms include:

• Itching or tingling of the lips, tongue, palate, or throat
• Mild swelling of the lips or inside the mouth
• A scratchy or “furry” feeling in the throat
• Occasionally, mild ear itching

These symptoms usually begin within minutes of eating the food and resolve within 15–30 minutes without treatment. Most episodes are mild. However, OAS should not be dismissed automatically — progression to more widespread symptoms, while uncommon, is possible and is discussed in the red-flag section below.

Why It Happens: Cross-Reactivity Between Pollen and Food Proteins

The underlying mechanism of pollen food syndrome is a phenomenon called cross-reactivity. Here is how it works in plain terms:

1. Pollen sensitisation comes first. If you have hay fever (allergic rhinitis), your immune system has already produced IgE antibodies against certain pollen proteins — for example, the PR-10 protein Bet v 1 found in birch pollen.
2. Food proteins look similar. Some raw fruits, vegetables, and nuts contain proteins that are structurally very similar to those pollen proteins. In the case of apple, the protein Mal d 1 shares approximately 65 per cent sequence identity with Bet v 1 (Allergy UK, 2025). This is the classic birch apple allergy pathway.
3. Your IgE antibodies cannot tell the difference. When you eat a raw apple, the Mal d 1 protein contacts the mucosal lining of your mouth and your birch-pollen IgE antibodies mistakenly bind to it, triggering a localised allergic response — the itching, tingling, and swelling you experience.

This explains two distinctive features of OAS:

• Cooking removes symptoms. The PR-10 proteins involved in most birch-related cross-reactions are heat-labile — they denature (break apart) at cooking temperatures. Once the protein changes shape, your IgE antibodies no longer recognise it, so baked apple, apple pie, and stewed apple are usually tolerated.
• Symptoms can be seasonal. Many people notice that their raw fruit reactions are more pronounced during or shortly after pollen season, when circulating IgE levels are higher. In the UK, birch pollen peaks between March and May (NHS, 2025).

Common Trigger Foods in the UK (and the Pollens Linked to Them)

The foods that trigger oral allergy syndrome depend on which pollen you are sensitised to. In the UK, birch pollen is the most significant driver of pollen food syndrome, but grass and other pollens can also play a role (BSACI, 2023).

Important notes: This table reflects commonly reported associations (BSACI, 2023; Allergy UK, 2025). Individual reactions vary significantly. Not everyone sensitised to a given pollen will react to all — or any — of the associated foods. Conversely, some people react to foods not listed here. Triggers should always be confirmed through clinical history, and where appropriate, targeted testing.

Notably, kiwi allergy can involve both pollen-related and latex-related cross-reactivity pathways, making it a particularly complex trigger food that may warrant component-level investigation.

How to Tell OAS From a ‘True’ Food Allergy

The term “true food allergy” is sometimes used informally to distinguish a primary, food-specific IgE-mediated allergy from pollen-driven cross-reactivity. Both are genuine immune responses, but the clinical implications differ:

The distinction matters because management differs. With typical OAS, many people can continue eating the cooked form of their trigger foods safely. With a primary food allergy involving heat-stable proteins, all forms of the food — raw and cooked — may need to be avoided, and an emergency action plan may be needed.

What Testing Can (and Cannot) Show: Specific IgE vs Component Testing

If your symptoms suggest oral allergy syndrome, IgE blood testing can provide useful information — but it is important to understand both its strengths and its limits.

Standard Specific IgE Testing

A specific IgE blood test measures your IgE antibody response to a whole allergen extract — for example, “apple” or “hazelnut”. A positive result indicates sensitisation: your immune system has produced IgE antibodies against that allergen. However, sensitisation does not automatically confirm clinical allergy. Many people with positive IgE results to a food tolerate that food without symptoms (NHS, 2025). Equally, in cross-reactive situations, a positive apple IgE may simply reflect your underlying birch pollen sensitisation rather than a separate apple allergy.

Component-Resolved Diagnostics (CRD)

Component testing goes one step further. Instead of testing against the whole allergen, CRD measures IgE against individual IgE proteins (components) within the allergen. For apple, this means the laboratory can test separately for:

• Mal d 1 — a PR-10 protein homologous to birch Bet v 1. Sensitisation to Mal d 1 is strongly associated with pollen food syndrome and usually indicates a lower-risk profile with mild oral symptoms.
• Mal d 3 — a lipid transfer protein (LTP). LTPs are heat-stable and digestion-resistant. Sensitisation to Mal d 3 is associated with a higher risk of systemic reactions and may indicate a primary food allergy rather than pollen-driven cross-reactivity.

This level of detail can help a clinician assess whether your sensitisation pattern is consistent with mild OAS (likely safe to continue eating cooked forms) or suggests a higher-risk profile that warrants further specialist evaluation.

What Testing Cannot Do

• A blood test result cannot diagnose oral allergy syndrome on its own. Diagnosis requires a clinician to interpret your IgE results alongside your symptom history, timing, and pattern of reactions.
• IgE levels do not reliably predict the severity of future reactions (NICE, 2025).
• A negative IgE result does not always rule out allergy — some people have clinically relevant allergies that are not well captured by standard IgE panels.

For more detail on reading your results, our guide to understanding kU/L and IgE levels on your lab report explains reference ranges, component results, and cross-reactivity patterns.

Practical Management: Food Prep Strategies, Antihistamines, and Risk Planning

If your clinician has confirmed or suspects oral allergy syndrome, the following practical strategies may help:

Food Preparation

• Cook, bake, or microwave. Heat denatures PR-10 and profilin proteins, so cooked, canned, or processed versions of trigger fruits and vegetables are usually tolerated.
• Peeling. In some cases, peeling fruit (e.g., apples, peaches) can reduce the allergenic protein load enough to prevent or lessen symptoms. This is not reliable for everyone but is worth trying if you wish.
• Choosing different varieties. Some people find that certain apple varieties (e.g., Granny Smith versus Gala) trigger worse reactions than others. This is not well studied, but individual experience can guide practical choices.

Antihistamines

Non-sedating antihistamines (such as cetirizine or loratadine) may reduce mild oral symptoms in some people, although evidence specifically for OAS is limited. They can be more helpful for managing concurrent hay fever symptoms. Antihistamines should not be used as a substitute for avoiding triggers that cause anything beyond mild oral discomfort.

Important Cautions

• Tree nuts and peanuts. While hazelnut and almond can be part of birch-related OAS, nut reactions carry additional risk because some people may also have primary nut allergies involving heat-stable proteins. If you react to any tree nut, this should be assessed by a specialist rather than managed on a self-directed basis.
• Soya and celery. These foods have been associated with more significant systemic reactions in the context of birch pollen cross-reactivity, particularly in concentrated forms (e.g., soya milk or celeriac). Caution is advised, and clinical guidance is recommended.
• Do not self-challenge with a food after any episode involving symptoms beyond mild oral tingling. Seek clinical guidance first.

What to Do If Symptoms Progress

• Spit out the food and rinse your mouth with water.
• If symptoms remain confined to the mouth and resolve within 30 minutes, no emergency treatment is usually needed.
• If symptoms spread beyond the mouth — for example, hives, abdominal pain, throat tightness, or difficulty breathing — follow the urgent help guidance in the red-flag box above.
• Keep a record of exactly what you ate, the timing of symptoms, and what happened. This information is invaluable for your clinician.

When to Get Assessed and What to Bring to Your Appointment

Consider seeking an allergy assessment if:

• You have consistent mouth or throat symptoms after eating specific raw foods.
• Symptoms are worsening, spreading beyond the mouth, or causing anxiety that affects your diet.
• You want to clarify whether your reactions are pollen-driven OAS or a primary food allergy.
• You react to tree nuts and want to know which specific nuts (if any) you need to avoid.

What to Bring or Prepare

• A symptom diary. Record the food eaten (raw or cooked), the exact symptoms, how quickly they appeared, and how long they lasted. Note whether the same food is tolerated when cooked.
• A trigger list. Write down every food that has ever caused oral symptoms, even if the reaction was mild.
• Pollen season notes. Note whether symptoms vary with the time of year — worse in spring (birch) or summer (grass).
• Photos. If you have ever had visible lip swelling or a rash around the mouth, photographs taken at the time of the reaction can help your clinician.
• Medication list. Include any antihistamines, nasal sprays, or other allergy medications you currently take.

Diagnostic-Only Testing at AllergyClinic.co.uk: What to Expect

At AllergyClinic.co.uk, we offer diagnostic allergy blood testing through nurse-led venepuncture. Here is what the process involves:

1. Appointment. A qualified nurse takes a blood sample at one of our clinic locations. The process is straightforward and typically takes a few minutes.
2. Laboratory analysis. Your blood sample is sent to an accredited laboratory for specific IgE testing. Depending on your request and clinical context, this may include whole allergen extracts, individual components, or both.
3. Report delivery. You receive a detailed laboratory report showing your specific IgE levels for each allergen tested, measured in kU/L.
4. Next steps. You take your report to your GP, allergist, or chosen clinician for interpretation. They will assess your results in the context of your clinical history and advise on management.

Please note: Our service is diagnostic sampling only. We do not provide clinical consultations, diagnosis, prescribing, or treatment plans. Your laboratory report should always be interpreted by a qualified healthcare professional who can consider your full medical history.

Questions to Ask After You Receive Your Report

When you take your allergy test report to your GP or specialist, these questions may help guide a productive discussion:

• Do my IgE results suggest pollen-driven cross-reactivity or a primary food allergy?
• Are there specific components (e.g., PR-10 vs LTP) I should be tested for to clarify my risk level?
• Which foods, if any, do I need to strictly avoid — and can I continue eating cooked forms?
• Do I need to carry an adrenaline auto-injector, or are my reactions consistent with low-risk OAS?
• Should I be referred to an NHS or private allergy specialist?
• Is there any benefit in repeat testing if my symptoms change over time?

Frequently Asked Questions

Is oral allergy syndrome the same as a food allergy?

Not exactly. Oral allergy syndrome is a form of IgE-mediated food allergy, but it is driven by cross-reactivity between pollen proteins and structurally similar proteins in certain raw foods. Unlike a primary food allergy — where the immune system responds to a food-specific protein — OAS occurs because your existing pollen-directed IgE antibodies also recognise similar proteins in food. Symptoms are usually mild and confined to the mouth and throat, whereas primary food allergies can cause more widespread systemic reactions.

Why can I eat cooked apples but not raw ones?

The proteins responsible for most OAS reactions — particularly the PR-10 family (such as Mal d 1 in apple) — are heat-labile, meaning they break down when exposed to high temperatures. Cooking, baking, or microwaving fruit typically denatures these proteins enough to prevent your IgE antibodies from recognising them. This is why many people with birch apple allergy can enjoy apple crumble or stewed apples without symptoms.

Can oral allergy syndrome cause anaphylaxis?

Severe systemic reactions from OAS are uncommon. Most people experience only mild, localised symptoms that resolve within minutes. However, rare cases of more significant reactions have been reported, particularly with certain foods such as soya, celery, or tree nuts. If you have ever experienced symptoms beyond mild oral tingling, you should discuss this with a qualified clinician to establish whether your reactions are truly limited to OAS or may represent a higher-risk primary food allergy (BSACI, 2023).

Does oral allergy syndrome get worse during hay fever season?

Many people notice that their food-related symptoms are more pronounced during or shortly after the pollen season relevant to their sensitisation pattern. For example, if you are sensitised to birch pollen (which peaks in March–May in the UK), you may find that raw apples, cherries, or hazelnuts trigger stronger mouth itching during spring. This is thought to be because circulating IgE levels increase during high pollen exposure (Allergy UK, 2025).

What is the difference between specific IgE testing and component testing for OAS?

A standard specific IgE blood test measures your IgE response to a whole allergen extract. Component-resolved diagnostics (CRD) goes further by measuring IgE against individual proteins — such as Mal d 1 (a PR-10 protein associated with mild pollen cross-reactivity) versus Mal d 3 (a lipid transfer protein associated with potentially more severe reactions). CRD can help a clinician distinguish between low-risk pollen-driven sensitisation and higher-risk primary food sensitisation (BSACI, 2023).

Can children develop oral allergy syndrome?

Yes. OAS can develop in children, particularly those who already have seasonal allergic rhinitis (hay fever). It tends to become more common from late childhood and into adolescence as cumulative pollen exposure increases. If your child reports consistent mouth itching after eating certain raw fruits or vegetables — especially during pollen season — it may be worth discussing with your GP or an allergy specialist (NHS, 2025).

Should I avoid all raw fruit if I have oral allergy syndrome?

No. Most people with OAS react only to specific fruits or vegetables that share proteins with the pollen they are sensitised to. You do not need to avoid all raw produce. A practical approach is to keep a symptom diary noting which specific foods trigger your reactions and discuss these with your clinician. Peeling fruit may also reduce symptoms in some cases.

Is oral allergy syndrome more common in the UK than other countries?

OAS patterns vary by region because they depend on which pollens are prevalent. In the UK and northern Europe, birch pollen is one of the most common sensitisers, making the birch–apple–hazelnut–cherry cross-reactivity pattern particularly common. In southern Europe, grass pollen and lipid transfer protein sensitisation are more prominent. Allergy UK notes that pollen food syndrome is now one of the most common food-related allergic conditions in UK adults.

Can peeling fruit reduce oral allergy syndrome symptoms?

In some cases, yes. Certain allergenic proteins are more concentrated in or near the peel of fruits such as apples and peaches. Peeling the fruit before eating may reduce the allergen load and lessen symptoms for some people. However, the PR-10 proteins most commonly involved in birch-related OAS are distributed throughout the fruit flesh as well, so peeling does not work for everyone. It can be a useful practical strategy, but it is not a substitute for clinical assessment if you are unsure about the nature of your reactions.

Do antihistamines help with oral allergy syndrome?

Non-sedating antihistamines (such as cetirizine or loratadine) may help reduce mild oral symptoms in some people, though evidence specifically for pollen food syndrome is limited. They are more commonly used to manage concurrent hay fever symptoms. Antihistamines should not be relied upon as a substitute for avoiding triggers that cause anything beyond mild oral discomfort (NHS, 2025).

Glossary

• IgE (Immunoglobulin E) — a type of antibody produced by the immune system. In allergic individuals, IgE antibodies bind to specific allergen proteins and trigger allergic symptoms upon re-exposure.
• kU/L (kilo units per litre) — the standard unit used to measure specific IgE levels in blood test results. Higher values indicate greater sensitisation, but do not reliably predict symptom severity.
• Cross-reactivity — when IgE antibodies originally produced against one protein (e.g., birch pollen Bet v 1) also bind to a structurally similar protein from a different source (e.g., apple Mal d 1), potentially triggering an allergic response.
• Component-resolved diagnostics (CRD) — an advanced form of IgE testing that measures antibodies against individual allergenic proteins within an allergen source, rather than the whole extract.
• PR-10 protein — a family of pathogenesis-related plant proteins. Bet v 1 (birch pollen) is the most studied. PR-10 proteins are heat-labile and typically associated with mild oral symptoms.
• Lipid transfer protein (LTP) — a family of heat-stable, digestion-resistant plant proteins. Sensitisation to LTPs is associated with a higher risk of systemic reactions compared to PR-10 proteins.
• Sensitisation — the presence of specific IgE antibodies against an allergen. Sensitisation indicates immune recognition but does not automatically mean you will experience symptoms on exposure.

Sources

• Allergy UK (2025). Pollen Food Syndrome Factsheet. Available at: www.allergyuk.org [Accessed 28 February 2026].
• Anaphylaxis UK (2025). Anaphylaxis: Recognition and Emergency Treatment. Available at: www.anaphylaxis.org.uk [Accessed 28 February 2026].
• BSACI (2023). Guidelines for the Diagnosis and Management of Pollen Food Syndrome. British Society for Allergy and Clinical Immunology. Available at: www.bsaci.org [Accessed 28 February 2026].
• Food Standards Agency (2025). Allergen Labelling and PPDS Guidance. Available at: www.food.gov.uk [Accessed 28 February 2026].
• NHS (2025). Food Allergy — Overview. Available at: www.nhs.uk [Accessed 28 February 2026].
• NICE (2025). Food Allergy in Under 19s: Assessment and Diagnosis. Available at: www.nice.org.uk [Accessed 28 February 2026].