ConditionMouth & teeth
Oral Allergy Syndrome (Pollen-Food Allergy)
Oral allergy syndrome (OAS), also called pollen-food allergy syndrome, is a reaction in the mouth and throat to certain raw fruits, vegetables and nuts in people with hay fever. Proteins in these foods resemble pollen proteins, so the immune system cross-reacts. Symptoms are itching or tingling of the lips, mouth and throat within minutes of eating, usually mild and short-lived. Cooking usually destroys the proteins, so the same foods are often tolerated cooked. A small number of people have more serious reactions.
Also called: Pollen-food allergy syndrome, PFAS, pollen-food syndrome, OAS
At a glance
- What it is
- Itching and mild swelling of the mouth and throat from raw plant foods that cross-react with pollen.
- Who gets it
- People with hay fever, especially to birch, grass or ragweed pollen.
- Common triggers
- Raw apples, pears, cherries, peaches, carrots, celery, hazelnuts, melons, bananas.
- Severity
- Usually mild and brief; a small minority have throat swelling or anaphylaxis.
- Management
- Avoid the raw food, eat it cooked or peeled, treat hay fever; carry epinephrine if advised.
When to get help
Call 911 or go to the ER
- Throat tightness, trouble breathing or swallowing, hoarse voice, wheeze, widespread hives, vomiting, or feeling faint after eating: use epinephrine if prescribed and call 911
See a doctor within a day or two
- Lip or tongue swelling that keeps increasing
- Symptoms beyond the mouth, such as hives, stomach pain or vomiting
- Reactions to cooked foods, nuts or soy
Book a routine appointment
- Repeated itching of the mouth after certain raw fruits or vegetables, to confirm the cause and assess risk
Usually safe to manage at home
- Brief, mild itching of the lips or mouth that settles within minutes after stopping the food
How oral allergy syndrome works
People with seasonal allergies make IgE antibodies against pollen proteins. Some raw fruits, vegetables and nuts contain proteins with a very similar shape. When eaten, these proteins contact the mouth lining and trigger a local allergic reaction. Most of these proteins are fragile: they are broken down by cooking, processing and stomach acid, which is why symptoms usually stay in the mouth.
Common pollen and food links
| Pollen allergy | Foods that may cause OAS |
|---|---|
| Birch (spring) | Apple, pear, cherry, peach, plum, apricot, kiwi, carrot, celery, hazelnut, almond, soy milk |
| Grass (summer) | Melon, watermelon, orange, tomato, potato, peach |
| Ragweed (late summer, fall) | Melon, watermelon, cantaloupe, banana, zucchini, cucumber |
| Mugwort | Celery, carrot, spices (fennel, coriander), peach |
Symptoms are often worse during pollen season. Latex allergy can cross-react with banana, avocado, kiwi and chestnut (latex-fruit syndrome).
Symptoms
Within minutes of eating the raw food:
- itching or tingling of the lips, tongue, roof of the mouth or throat
- mild swelling of the lips, tongue or throat
- itchy ears
- sometimes sneezing or watery eyes
Symptoms usually fade within 15 to 30 minutes after the food is removed or swallowed.
When it is more serious
A small proportion of people have reactions beyond the mouth, including throat swelling or anaphylaxis. Higher-risk features include:
- reactions to cooked foods
- reactions to nuts, especially peanuts and tree nuts
- previous systemic symptoms (hives, vomiting, breathing difficulty)
- reactions to foods that are not typical pollen cross-reactors, which may indicate a different, more stable food allergen (such as lipid transfer proteins)
Diagnosis
An allergist will take a detailed history of foods, symptoms and pollen allergies. Tests may include:
- skin-prick tests with pollen and with fresh fruit or vegetable ("prick-to-prick")
- specific IgE blood tests, including component testing (for example birch Bet v 1-related proteins versus lipid transfer proteins), to assess risk
- supervised oral food challenge if the diagnosis or risk is unclear
Management
- Avoid the raw trigger foods that cause symptoms.
- Cook, bake, microwave or can them: heat usually breaks down the allergen. Applesauce, apple pie or canned peaches are often tolerated.
- Peel fruits such as apples and peaches, as more allergen is in the skin.
- Treat hay fever with antihistamines and nasal steroids; this may reduce OAS symptoms during pollen season.
- Oral antihistamines for mild mouth symptoms.
- Epinephrine auto-injector for people at higher risk, as advised by an allergist.
- Allergen immunotherapy for pollen may improve OAS in some people, though results are inconsistent.
Frequently asked questions
What foods cause oral allergy syndrome?
Common triggers are raw apples, pears, cherries, peaches, kiwi, carrots, celery, hazelnuts and almonds (linked to birch pollen), and melons, bananas and cucumbers (linked to ragweed). The specific foods depend on which pollens you are allergic to.
Why can I eat cooked apples but not raw ones?
The proteins that cause oral allergy syndrome are fragile and are broken down by heat. Cooked, baked or canned fruit usually does not trigger symptoms, even when the raw fruit does.
Is oral allergy syndrome dangerous?
Usually not. Most reactions are limited to brief mouth and throat itching. A small number of people have more serious reactions, especially with nuts or cooked foods. An allergist can assess your risk.
Can oral allergy syndrome go away?
It can fluctuate with pollen seasons and may improve with hay fever treatment or allergy shots, but it often persists. New trigger foods can appear over time.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Allergy, Asthma & Immunology: Oral allergy syndrome (pollen food allergy syndrome)
- American College of Allergy, Asthma and Immunology: Oral allergy syndrome
- Food Allergy Research & Education (FARE): Oral allergy syndrome
- NHS: Food allergy
- Anaphylaxis UK: Pollen food syndrome