Skin prick tests (performed in duplicate) were considered positive when mean wheal diameter >3 mm. Allergic symptoms were reported in diary cards during the relevant pollen season. Symptoms were considered as pollen allergy when lasting > 7 days or when symptoms were repeatedly elicited when pollen counts exceeded a certain (individual) level . The skin prick test was performed according to the guidelines of European Academy of Allergy and Clinical Immunology . n = 10 for the healthy controls, n = 10 for the asymptomatically sensitized individuals and n = 8 for the allergic individuals.