Birch

Occurs in Europe, Siberia, Asia Minor; North Africa; Scandinavia; widely used deciduous trees.

Main allergen (major allergen) is antigen 23 (M 17 kDa, pl 5.25), according to WHO nomenclature: Bet v 1 (stands for Betula verrucosa). Bet v1 stands for a superfamily of proteins, the Bet v1 superfamily, which currently comprises around 23,600 members. These proteins, which are found in all three domains of life ( archaea, bacteria, eukaryotes) are based on the typical Bet v-1 architecture.

The second allergen (minor allergen) was Bet v 2 (protein of the profilin family).

Among the tree pollen, birch pollen are the most aggressive allergens. The threshold value for triggering an allergic reaction is 76 pollen per m3. The immunodominant birch pollen allergen Bet-v1 is involved in the natural defence of plants (pathogenesis-related protein family 10 also known as PR-10 protein). Similar proteins are not only found in other pollen plants (e.g. hazelnut, alder, beech, oak) but also in numerous fruit and vegetable varieties, as well as in nuts and legumes. They are the basis for the cross-reactions observed in birch pollen allergy sufferers, e.g. to apples (see below apple allergy) and pears (e.g. birch pollen-nut-nut-fruit syndrome). Due to the heat and lability of the allergens in the gastric environment, these are generally limited to the oral cavity(oral allergy syndrome).

Apparently, non-allergenic low-molecular substances such as different types of allergens play a role. Sugars, fatty acids and nucleosides of birch pollen (Bet-APE<3kDa) seem to play a role as an enhancer of the allergic reaction (Clin Exp Allergy 2016).

The leaves are used medicinally, whereby the young leaves are particularly rich in active ingredients (see Betulae folium below ). Birch tar (see Pix betulina below) is extracted from the bark.

19-25% of pollinators in Central Europe are sensitized to birch pollen (see below pollen; see below tree pollen). Birch pollen allergy sufferers react particularly frequently (30-70%) to food (see cross-reaction below). The most frequent cross allergies are to stone and pome fruit (especially apple; see below apple allergy), soya (Gly m4), nuts, raw vegetables (especially carrots), celery (Api g1), less frequently to Brazil nuts and peppers. These food allergies often manifest themselves as " oral allergy syndrome". In rare cases, birch pollen allergy sufferers develop contact urticaria caused by birch branches. A worsening of atopic eczema (freely carried skin areas) associated with birch pollen is questionable.

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   in vivo. Clin Exp Allergy doi:10.1111/cea
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