Objective: To determinate the existence of associations among sensitizations to antigens produced by pollen grains of different botanical species as assessed by skin prick tests in patients with respiratory disorders.

Methods: Six hundred twenty nine consecutive patients living in the northern area of Madrid who underwent clinical evaluation because of rhinoconjunctivitis, and/or asthma were studied. All patients were tested with a skin prick test using a battery of inhalants including pollens, dust mites, molds and danders. The exploratory multivariate technique of Multiple Correspondence Analysis was used to compare the homogeneity of sensitizations between groups. Of the 629 patients, 459 (73.0%) had positive skin prick tests to pollen and were selected as the study group.

Results: The most prevalent pollen sensitization was to Gramineae pollen (83.7%) followed by Oleaceae sensitisation (75.8%). Multiple Correspondence Analysis revealed the existence of an association among pollen sensitizations, showing that they clustered two groups: sensitizations to Gramineae, Oleaceae, Cupressaceae, Chenopodiaceae, Plantaginaceae (group I), and sensitizations to Betulaceae, Platanaceae, Compositae (group II). Sensitization to Parietaria was not included in any of the sensitization groups and showed an independent behaviour.

Conclusion: Pollen sensitizations in our area cluster into two association groups which have not previously been reported.

Key Words: Pollen. Pollinosis. Allergens. Sensitizations. Association.