Anyone allergic to birch and other tree pollen often responds to certain foods due to a cross-reaction.

Woman with apple - Cross-reactions - aha! Swiss Allergy Centre - Info on allergies - © Image: iStock_000016313550XSmall

This cross-reaction (or pollen-associated food allergy) can be explained by the fact that pollen and food allergens are similar in structure and so are mistaken for each other by the immune system. Sufferers generally have mild symptoms such as itching, redness and mild swelling in the mouth and throat.

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What is a cross-reaction?

In this form of food allergy, the respiratory tract (nose, lungs) first becomes sensitised to birch pollen, for example. Because the protein structures of inhalation and food allergens are similar, this results in a cross-reaction, or pollen-associated food allergy.

Birch pollen-nut-pip fruit or mugwort-celery spice syndrome are common examples of a cross-reaction. Therefore someone who has become sensitised to birch pollen may also have an allergic reaction to apples and nuts and vice versa.

There are other respiratory tract allergens apart from pollen that may cause a cross-reaction to foods, e.g. latex (natural rubber), animal allergens (e.g. cats, birds) and house dust mites.


How can a cross-reaction be identified?

Sufferers from pollen allergy who experience a tingling in the palate, burning and itching in the mouth area and lips or even develop swelling affecting the face when eating certain foods should consider that they may have a cross-reaction.

How can they be prevented?

Anyone who notices tingling/burning in the mouth or throat should no longer consume the food concerned. Admittedly, a lot of proteins are destroyed by cooking and heating and the food can be eaten again. A frequent recommendation is to eat only small amounts of the food in question. Occasionally pollen therapy by means of desensitisation will also relieve the food allergy.

What are the most common cross-reactions?

Around 70 per cent of people who suffer from tree pollen allergies are found to have cross-reactions with foods. Cross-reactions are less common with other types of pollen and respiratory tract allergens. The following are typical:

Birch, alder, hazel pollen (january–april)

Stone and pip fruit (apples, pears, plums, apricots, cherries, etc.), hazelnut, walnut, almonds, tomatoes, carrots, celery, mango, avocado, fennel, kiwi fruit, lychee

Mugwort pollen (Artemisia vulgaris) (july–August)

Celery, carrots, fennel, artichokes, camomile, pepper, mustard, dill, parsley, coriander, caraway, aniseed, sunflower seeds.

House dust mites

Prawns, lobster, langoustine, crab, snails


Avocado, bananas, sweet chestnut (vermicelli, roasted), kiwi fruit, papaya, figs, paprika

Bird feathers

Chicken eggs (yolk)

Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board. For prevalence figures, see source references.

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