A very risky 'relationship', pollen-food, which if you don't know and are allergic can be dangerous. Immunologist Mauro Minelli, responsible for the South of the Foundation for Personalized Medicine (Fmp), explains how this 'marriage' can end badly. A peculiar characteristic of allergies is that of generating, in predisposed subjects, even rather severe clinical pictures – from rhinitis to asthma, from urticaria to eczema and even anaphylaxis – through immunological mechanisms activated by substances that are completely harmless to the non-allergic population”, says the immunologist to Adnkronos Salute.
“Classically, these substances include dust and pollen, foods and drugs, nickel and other metals, animal dander and mold. Over time, however, it has been seen – he observes – that the antigens responsible for common allergic reactions can present, in percentage variable, a structural and biochemical homology with other protein molecules widespread in the plant and animal world, which perform functions of a different nature (defensive, structural enzymatic). These proteins are present in pollen, in foods of the plant kingdom (fruit, vegetables, seeds). , in foods of the animal kingdom (milk, eggs, meat, molluscs), in different organisms (mites, snails, cockroaches, worms)”.
The World Health Organization now considers allergy a “non-communicable, out-of-control disease. And, on the other hand, the last ten years have seen a marked increase in allergies in all countries of the world, almost reaching, in some of these, a prevalence of 50% in the last generation”, recalls Minelli.
Pollen, foods and allergies
“In particular, it was found that, when a molecule presents a high allergological homology with other molecules, the patient, in addition to showing sensitization to the primary molecule, can also be allergic to the homologous molecules. This finding – continues Minelli – he clarified why a subject allergic, for example, to apple pulp often turns out to be allergic to birch pollen, despite never having had the opportunity to become aware of the birch tree. In reality the patient could be allergic to the Pr proteins (Pathogenesis Related proteins) present, in high homology, both in the apple pulp and in the birch pollen. These are rather labile proteins (thermo- and gastrolabile) so foods containing them, if cooked or otherwise subjected to re-elaboration processes (jams, fruit juices), are generally well tolerated”.
In this case the patient “could also be allergic to all other pollens and foods containing Pr-proteins, certainly present in birch pollen (Bet v 1 molecule), but also in many foods belonging to the Rosaceae families (apple, pear, peach, apricot, cherry, plum, plum, almond, medlar), Apiaceae (celery, carrot, fennel, parsley, anise), Fabaceae (bean, pea, broad bean, lupin, peanut, soya, lentil), Poaceae (wheat, corn , barley, oats, rye)”, he specifies. These cross-allergic reactions occur in those subjects who present “a sensitization towards homologous proteins contained both in pollen and in foods. The phenomenon, defined as 'cross-reactivity' but better identified with the term 'co-recognition', explains why some patients may experience even severe reactions by taking allergenic foods they have never before ingested”, warns the immunologist.
“The cause of all this is to be found in the botanical 'relationship' between the pollen of some families and various foods: the immune system also reacts to the substances contained in foods, due to their affinity with the antigens contained in inhaled pollen. to their diffusion – Minelli summarizes – scientific studies conducted on the subject have shown that, in a large population of 25 thousand allergic people, 55% of food allergies are due to a cross-reaction between pollen and food“.
“Wanting to further broaden the field of cross-reactivity, it is possible to refer, for example, to the fact that a significant portion of patients allergic to birch pollen, grasses or other herbs (including ragweed or mugwort or parietaria) it reacts not with pollen as such, but with profilin, a protein present in pollen grains and cross-reacts with many other profilins present in foods of plant origin. This eventuality – the immunologist points out – justifies any reactions produced by tomatoes, melons , kiwi or orange, in subjects allergic to grasses; or reactions produced by mulberry, basil, cherry or melon, in subjects allergic to parietaria; or reactions produced by melon or banana, in subjects allergic to ragweed”.
“Just as it justifies reactions produced by pepper, celery, pineapple or banana in subjects sensitive to Hev b8 which is a molecular fraction of latex belonging to the profilin family, as well as other molecular fractions of latex, such as Hev b11 or Hev b2, or Hev b5 or Hev b6, may be responsible for reactions produced by other cross-reacting foods within the so-called 'Latex Fruit Syndrome' – he concludes – The phenomenon of cross-reactivity has clarified again why a subject allergic to peach which contains a protein from the Ltp (Lipid Transfer Protein) group, is often also allergic to grapes, apples or hazelnuts. Those belonging to the Ltp group are allergens resistant to heat and digestion in the gastrointestinal tract, this which allows them to also induce important generalized symptoms up to anaphylactic shock”.
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