Cross-reactions

It is often the case that someone who has a reaction to tree pollen, animals or latex is also unable to tolerate certain foods due to a cross-reaction.

Kiwi

This cross-reaction can be explained by the similarity in structure of, for example, pollen and food allergens, which are then mistaken for each other by the immune system, resulting in a cross-reaction. Sufferers generally have mild symptoms such as itching, redness and mild swelling in the mouth and throat.

Causes and triggers

In this secondary food allergy, the respiratory tract (nose, lungs) first becomes sensitised to birch pollen, for example. Because the pollen allergen is similar in structure to certain proteins in fruit, vegetables and nuts, the immune system confuses the one with the other and suddenly also reacts to certain foods. Such cross-reactions are not uncommon; approximately 70% of those allergic to tree pollen are also allergic to certain foods.

Two cross-reactions are particularly common: birch pollen-nut-pip fruit and mugwort-celery spice syndrome.

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.

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
 

Latex

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

Bird feathers

Chicken eggs (yolk)
 

Symptoms

Typical symptoms when eating certain foods are a tingling sensation in the palate, burning and itching in and around the mouth and lips and may even include swelling in the face. This is often known as oral allergy syndrome. The symptoms usually soon disappear.

Treatment

In principle, it is best to avoid eating whatever foods cause symptoms. However, this is not so straightforward in practice. For example, some allergens are destroyed when cooked or heated, which means that the foods in question can then be eaten. The foods may also be tolerated if eaten in small amounts. Moreover, individual foods are better tolerated outside the pollen season.

Should it nonetheless happen that something is eaten that causes symptoms, then anti-allergy medication such as antihistamines can be helpful.

Occasionally pollen therapy by means of desensitisation will also relieve the food allergy.

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