Features of sensitization to airborne allergens among extra-European immigrants living in 2 distinct areas of Northern Italy.

BACKGROUND Extra-European immigrants are increasingly seen in allergy clinics. In view of their different genetic background they represent an opportunity to investigate the dynamics of sensitization to airborne allergens. OBJECTIVE We investigated the pattern of airborne sensitization among allergic extra-European immigrants living in two areas of northern Italy. METHODS Extra-European immigrants living in Milan and Verona were compared with age- and sex-matched or allergen-matched allergic Italians. Based on number of sensitizations to airborne allergens, patients and controls were divided into mono-/oligo-sensitized or multi-sensitized (1-3 or > 3, respectively). RESULTS In Milan grass pollen allergy was more frequent among immigrants than in controls (75% vs 49%; p < 0.01), whereas ragweed allergy prevailed among Italians (56% vs 20%; p < 0.001). In Verona, immigrants were rarely multi-sensitized (21% vs 43%; p < 0.01), more frequently sensitized to grass and birch. In both areas immigrants became allergic at a significantly older age than Italian controls (p < 0.0001), particularly to grass and mites. Allergy to HDM and ragweed was rare in Central & South Americans, whereas Africans showed the lowest proportion of multi-sensitizations. On average, immigrants became allergic after 2-4 years of stay in Italy. CONCLUSION Subjects genetically prone to become allergic to a particular allergen get eventually sensitized irrespective of their age when they are exposed to the "right" allergen for a sufficiently long time. The higher proportion of mono-/oligo-sensitized immigrants might reflect a shorter exposure to airborne allergen load in this group.