Background: Olive pollen sensitization is surprisingly frequent in Milan, an area that is virtually both olive- and ash-free.
Objective: To establish the prevalence of olive pollen sensitization north of Milan, and to investigate the allergens involved.
Methods: 300 pollen-allergic patients living in this area were randomly selected. Based on SPT results, olive pollen reactors were classified as multi-sensitized, oligo-sensitized, or mono-sensitized. IgE to markers of primary sensitization to olive pollen (Ole e 1), as well as to pollen pan-allergens such as profilin (Phl p 12) or polcalcin (Phl p 7) were measured. Further, the putative cross-reactivity between grass group XI allergen and Ole e 1 was investigated.
Results: 107 (36%) patients were sensitized to olive pollen; 67 (63%) were multi-sensitized, while only 4 (4%) were mono-sensitized. Specific IgE to Ole e 1 were found in 32/46 (70%) cases; 22 of them (69%) co-recognized pollen pan-allergens, as shown by IgE reactivity to Phlp 7 and/or Phlp 12. Sera from 14 (30%)patients did not react to Ole e 1; of these, 10 (71%) were pan-allergens reactors. No correlation was found between IgE levels to Phl p 11 and Ole e 1.
Conclusions: A majority of olive pollen-sensitized subjects seen in the surroundings of Milan are truly allergic to Oleaceae. In the absence of both olive and ash trees exposure to privet pollen might represent the source of this kind of sensitization.