Standardized extracts, trees.

Sensitization to pollen from wind-pollinated trees causes significant allergy problems during springtime. The magnitude of prevalence is comparable with and, in some areas, even higher than grass pollen allergy. The symptom periods are often prolonged by cross-reactivity among species and sometimes families as well as by simultaneous sensitivity to several trees, pollinating at different times. There is a need for standardized extracts to improve diagnostic precision and treatment efficacy. A substantial amount of immunochemical data on the allergens from Betulaceae species, particularly Betula (birches), are available. Relevant methods to quantitatively and qualitatively measure the allergens of birch pollen extracts are clearly reproducible in laboratories around the world. By international collaboration, such work has generated an IS that has been accepted by the IUIS Subcommittee on Allergen Standardization. The IS is a yardstick for authorities, manufacturers, and researchers that is carefully specified in terms of 1 major and a few intermediate allergens, and also of total biologic activity by RAST inhibition. A meaningful declaration of biologic activity in vivo is awaited. As yet, only a few clinical trials have been undertaken with standardized tree pollen extracts. These are, however, highly interesting, particularly those that now have started with an oral route of administration.