Of 33 patients who had been initially screened, ten patients did not fulfill all of the inclusion criteria mentioned hereafter. Thus, 23 patients aged 18 to 67 years having a birch and/or grass pollen allergy were included in the analysis. The study is in line with the Declaration of Helsinki and is approved by the responsible ethics committee (FF 118/2012 (4 December 2012); Landesärztekammer Hessen, Frankfurt, Germany). All participating patients are informed of the nature and objectives of the study and signed an informed consent document.