Pollen from various Fagales tree species prolong the season and make tree pollen allergy a major health problem. A new article published in Allergy reported on a discussion by medical experts on the diagnosis and treatment of allergy immunotherapy (AIT) in patients allergic to tree pollen, who also provided practical recommendations based on the available data. This article reported that according to current guidelines on allergen products, birch is the representative allergen source of the birch homologous group, including several Fagales trees, based on sequence and structural similarity of their allergen proteins. A high level of immunoglobulin (Ig)E cross-reactivity towards allergens from the birch homologous group has been observed in basic research and clinical trials. While clinical trial data show that the efficacy of birch AIT is not only related to birch pollen allergy, but extends to other trees, especially alder, hazel and oak. In order to optimize diagnosis and treatment of tree pollen allergy the experts recommended focusing on diagnosis and respective treatment with AIT, primarily to birch as the representative allergen of the Fagales tree homologous group. However, for some patients, further diagnostic tests may be necessary to determine adequate treatment.