BackgroundThe prevalence of allergic diseases has increased for several decades. During the last years there is a possible change in the pattern of sensitization to different aeroallergens in atopic patients.ObjectivesThe aim of this study was based on the hypothesis that during last twenty years there has been a change in the structure of prevalence of sensitization to pollens in atopic patients.Patients and methodsIt wasa prospective study including patients with allergic diseases, who were diagnosed from 1995 to 2014. Skin-prick tests (SPT) were performed with common aeroallergens. We compare the results of SPT on two different periods of 10 years each, a first period (P1) from 1995 to 2004 and a second period (P2) from 2005 to 2014.ResultsWe included 8807 patients during last twenty years with 4818 (54.7%) positive SPT. The average age of patients with a positive SPT was 24.4 years with a sex ratio of 1.3. Proportion of positive SPT significantly increased from P1 to P2 (47.3% vs 65.4%, p<10-6). The sensitization rate to pollen, in this last twenty years was 44.1%. Proportion of sensitized individuals to pollen significantly increased from P1 to P2 (38.6% vs 49.7%, p<10-6) with a significant increase in the proportion of sensitized individuals to tree pollen (12.7% vs 18.5%, p=10-6) and grasses pollen (14.6% vs 18.2%, p=6 10-3), while the proportion of sensitized to weed pollen decreased (15.4% vs 6%, p=10-6). Among tree pollens, skin reactivity to cypress pollen increased significantly (5.6% vs 12%, p=10-6).ConclusionWe found a significant change in the proportion of sensitization to different pollen groups and individual pollen species during the investigated two last decades.