Background: Some studies have suggested that specific immunotherapy (SIT) may cause de novo sensitization to allergenic proteins to which patients were not previously allergic. This event might theoretically involve cross-reacting pollen allergens, such as profilin or polcalcins, posing a risk of SIT-induced polysensitization to pollens in patients who were originally monosensitized.

Objectives: The aim of this study was to assess whether injection SIT with commercial pollen extract represents a risk factor for the de novo development of sensitization to different pollens in monosensitized patients.

Methods: The study involved 142 subjects diagnosed as being monosensitized to a single pollen: 64 patients who were administered a 3-year course of injection SIT and 78 controls. Subjects underwent control skin prick tests (SPT) with a series of 8 seasonal airborne allergens at least 3 years after the first visit. Patients with 5 or more new
sensitivities on SPT were considered to be de novo polysensitized.

Results: At the end of the 3-year follow-up period, the proportion of polysensitized subjects was identical in previously monosensitized patients who underwent SIT and control individuals (11% and 10%, respectively). Individuals who were polysensitized were significantly younger than those who were not (mean age ± SD, 21.6 ± 11.0 years vs 31.6 ± 15.6 years; P < .05).

Conclusion: SIT does not represent a risk factor for progression towards multiple pollen sensitization in monosensitized pollen-allergic patients.

Key words: Pollen. Specific immunotherapy. Calcium binding proteins. Profilin. Cross-reactivity.