R. Asero AmbulatoriodiAllergologia,ClinicaSanCarlo,PadernoDugnano(MI),Italy-E-mail:r.asero@libero.it RagweedallergyinnorthernItaly:arepatternsof sensitizationchanging? Summary Background: Previous surveys performed in this area showed that the age at onset of ragweed allergy in monosensitized subjects is about 35. Objective: To detect whether a reduction in the mean age of ragweed sensitization in the area of Milan has taken place after the last survey. Methods: All patients developing clinical ragweed pollen allergy in the years 2007-2010 and monosensitized to this allergen seen were included. 30 ran- domly selected subjects already sensitized to at least one other allergen source among grass, pellitory, or mite who developed ragweed allergy during the same period served as con- trols. Results: The 137 patients showed a median age at onset of ragweed allergy of 36- 40 years in the years 2007-2010 with no tendency to reduction. About 10% of patients were < 20 years old in 3 of the 4 study years. 15% of patients were > 50 years old at on- set, and 3 of them were > 70. In the control group the mean age at onset of ragweed al- lergy was 31,6 years (median 32,5 years; range 10-60; p< 0.001 vs patients). Conclu- sion: In this area monosensitization to ragweed occurs steadily at an adult age. In al- ready allergic subjects it occurs at a younger age. The age at onset of allergy to one specific airborne allergen source seems to depend on several variables, including exposure dura- tion, atopic status, and specific features of the allergen. Key words Ragweed, pollen allergy, respiratory allergy Corresponding author Dr.RiccardoAsero AmbulatoriodiAllergologia ClinicaSanCarlo PadernoDugnano(MI),Italy E-mail:r.asero@libero.it Introduction Following its timid appearance at the end of the ‘80s (1,2),overthelast20yearsragweedhasgraduallybecome the second most frequent cause of respiratory allergy in NorthernItalyandbyfartheonecausingthemostsevere symptoms. At the beginning of this century one study from this allergy centre noted that in the area north of Milan ragweed allergy showed a curious but typical pat- tern, as de novo sensitization occurred mostly in subjects that lacked a familiar history of atopic diseases and were much older than those developing allergies to other air- borneallergens(3).Themeanageatonsetofragweedal- lergicpatientsinthisareawasaround35years.Inasub- sequent longitudinal retrospective study examining ragweed monosensitized patients seen at this allergy cen- trefrom1990to2006(4)itwasnotedthatthemeanand median age at onset had remained virtually unchanged over the years, the only change being the proportion of patients aged < 20 years that showed a trend on the rise. Based on those results it was hypothesized that a gradual reduction in mean age at onset of clinical allergy to ragweed might have been expected in the forthcoming years.Thedatarecordedduringthelast4yearsandanaly- sed using the same criteria are reported here. The study aimed to detect whether a reduction in the mean age of Eur Ann Allergy Clin Immunol VOL 44, N 4, 157-159, 2012 ORIGINAL ARTICLE