Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms.

Trees within the order Fagales possess particularly potent allergens, e.g. the prototypical Bet v 1, the major white birch (Betula verrucosa - now called B. pendula) pollen antigen.

However, one very striking feature of the three-dimensional structure of Bet v 1 is the presence of a large hydrophobic cavity, which is open to the exterior and probably functions as a ligand binding site.

It belongs to the pathogenesis-related (PR) proteins, which are usually expressed upon infections and stressful conditions,[7] implicating a role in host defense.

In vitro, Bet v 1 has been shown to be immune-suppressive, due to its ability to bind to iron-flavonoid complexes, which it can shuttle into human monocytic cells to increase their labile iron pool and stimulate the anti-inflammatory Arylhydrocarbon receptor pathway (https://www.mdpi.com/2076-3921/12/1/42).