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.