Abstract Detection of specic IgE using component resolved diagnostics (CRD) identies the underlying allergen source in suspected cases of tree and grass pollen allergy. Suitable marker allergens can be used to dis-tinguish genuine sensitization to tree or grass pollen from cross-reactivity to pollen panallergens (e. g. pro-lin and polcalcins) and to overcome the lack of an-alytical specicity of natural allergen extracts. In pa-tients reacting with a variety of pollen extracts sus-pected of polysensitization, CRD allows allergen spe-cic diagnosis regardless of the confounding e ect of panallergenic cross-reactivity and administration of tailored, specic immunotherapy. In this article, allergens indicating specic sensi-tization to grass and tree pollen are described. Allergens dened as marker allergens for tree and grass pollen allergy are Bet v 1 (birch pollen major allergen) for birch, beech and other trees from the Fagales order, Ole e 1 (olive pollen major allergen) for olive and other trees including ash from the Oleaceae family, Pla a 1 (major allergen of the Lon-don plane tree) for plane trees, Cry j 1 (major aller-gen of the Japanese cedar), Cup a 1 (major allergen of the Ari zona cypress) for cypress trees and Phl p 1 und 5 (Timothy grass major allergens) for sweet grasses including rye. Grass and tree pollen aller-gens with serological and clinical cross-reactivity to a great number of allergen sources are also identi-ed as possible confounding factors in allergen spe-cic diagnosis with natural extracts. Structured dia-gnostic procedures for clinical routine work are pro-posed.