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Oral Allergy Syndrome

As if having hayfever itself wasn’t bad enough, Oral Allergy Syndrome or Pollen-Food Syndrome typically occurs in people afflicted with hayfever triggered by tree pollen (birch and alder), grass pollen and to ragweed, an allergen well-known in the US and the latest to make its presence felt in the UK.

The symptoms appear within moments of eating certain fruits and vegetables and are typically experienced as an itchy tongue and roof of the mouth, itchy or burning lips, mouth or throat.


Cross-reactors with TREE POLLEN (typically birch and alder)

Fruits: Apple, Apricot, Cherry, Fig (still being studied), Kiwi, Lychee, Nectarine, Pear, Plum, Peach, Prune, Persimmon, Strawberry, Tomato

Vegetables: Beans, Carrot, Celery, Green pepper, Potato, Parsnip, Peas

Nuts: Almond, Hazelnut, Walnut

Herbs & Spices: Anise, Basil, Dill, Caraway, Chicory (early evidence only), Coriander, Cumin, Fennel, Marjoram, Oregano, Parsley, Paprika, Pepper, Tarragon, Thyme

Others: Lentils, Peanut, Soybean, Sunflower seeds

Cross-reactors with GRASS

Fruits: Date, Fig (still being studied), Kiwi, Melon and Watermelon, Orange, Tomato

Vegetables: Peas, Potato

Others: Peanut

Cross-reactors with MUGWORT (common in Europe & Asia)

Fruits: Apples, Melon & Watermelon, Orange, Peach, Tomato

Vegetables: Carrot, Celery, Green pepper, Onion, Parsnip

Herbs & Spices: Anise, Basil, Caraway, Coriander, Dill, Fennel, Marjoram, Mustard, Oregano, Paprika, Parsley, Pepper, Tarragon, Thyme

Other: Chamomile, Sunflower seeds

Cross-reactors with RAGWEED (pollinates in Autumn)

Fruits: Banana, Melons & Watermelons

Vegetables: Courgette, Cucumbers

Fortunately the reactions are not a real life-threatening problem like true food allergies and the symptoms usually subside within fifteen minutes or so. However If someone gets more severe reactions such as swelling of the mouth, back of the throat and windpipe and the appearance of hives with both fresh and cooked fruit, vegetables or nuts, or if symptoms are prolonged (hours instead of minutes), this may be the sign of a true food allergy..

People with OAS are often allergic to heat-labile protein, those proteins easily destroyed by heat. So though they will react to eating raw fruit and vegetables, are usually able to eat the same food when it’s been cooked, without a problem. This is why when you eat fruit raw and your own body’s heat breaks down the protein, the reaction doesn’t move beyond the mouth.

Awareness of Oral Allergy Syndrome is growing and your GP may be alert to the symptoms and make a diagnosis, but how can you be sure if you have it?

Since it occurs mainly in people with allergies to birch, grass or ragweed pollen, the key to diagnosis is a history of hayfever and positive skin tests to relevant pollens plus a history of eating the food with typical mouth and throat symptoms without other symptoms. The ability to eat the cooked variety of the fruit or vegetable makes the diagnosis fairly certain.

Sometimes a person may not react to say, any of the vegetables sharing allergenic proteins with birch tree pollen, only to fruits. This could be due to a lower level of offending proteins in some of the cross-reacting foods. Freshness also makes a big difference to the potency. Peel also tends to have more protein than the fruit itself so if you peeled an apple and ate it, you might not react as if you ate one with the peel on. Sprinkling cut-up fruit with lemon juice and letting it sit for a few minutes may help as can microwaving raw fruit before eating.