Pollen-associated food allergy (cross-allergy)

In a pollen-associated food allergy, IgE antibodies originally produced against pollen also target similarly structured proteins in plant foods. This is called a cross-reaction or cross-allergy; the reaction in the mouth is called oral allergy syndrome. The sensitisation is measured in serum, in the test catalogue as “pollen-associated food intolerance” (pollenassoziierte NMU) in Vorscreen B, together with IgE and IgG4 antibodies to foods and DAO. Which allergen groups were tested is stated in the report. IgE to foods in general is explained on a page of its own.

How the cross-reaction between pollen and foods arises

Plants produce defence and structural proteins that are very similar across species. The main birch pollen allergen Bet v 1 belongs to the PR-10 protein family; closely related proteins are found in apple (Mal d 1), hazelnut (Cor a 1), cherry (Pru av 1), carrot (Dau c 1), celery (Api g 1) and soy (Gly m 4). If the immune system has formed IgE against Bet v 1 via the airways, these antibodies also recognise the related food proteins. Other cross-reacting groups are the profilins, which occur in almost all pollen and many plants, and allergens from mugwort and grass pollen. On the mast cells, the food protein then binds the IgE and triggers the release of histamine.

Pollen-associated sensitisation detected – what happens in the body?

A positive result means that antibodies against cross-reacting plant proteins are present. PR-10 proteins and profilins are quickly destroyed by heat and stomach acid. That is why it is mainly the mucous membranes of the mouth and throat that react, as they are the first to come into contact with the raw food: tingling, itching and swelling of the lips, tongue and palate usually occur within minutes. Cooked or baked fruit and vegetables are often tolerated. During the pollen season the immune cells are more strongly activated, and symptoms may then increase. Rarely, reactions are stronger, in case reports for instance after large amounts of soy drink. Sensitisation is not the same as an allergy: not every positive result leads to symptoms.

Pollen-associated sensitisation not detected – what does it mean?

If no antibodies against the tested cross-reacting allergens are detected, a pollen-related cross-reaction as the reason for symptoms after raw fruit, vegetables or nuts is less likely. Allergies to heat-stable proteins, such as storage proteins in nuts or lipid transfer proteins, are captured via other allergen groups and are not affected by this. Nor does this value show symptoms without IgE involvement – for example due to histamine, fructose, sorbitol or additives. Together with IgE to foods, IgG4 and DAO in the Vorscreen, it helps to assess which reaction pathway fits the symptoms.

The interpretation is given in your report.