In a multi-centre study, comprising 16 clinics, 871 adult hay fever patients were studied. Most patients included had springtime hay fever. Skin prick tests were performed with 20 different tree or bush pollen (lignoses) allergens. RAST determinations were done with eight different tree pollen allergens in 590 patients. Birch pollen (BP) allergen gave the highest frequency of positive test results. The test results with the various tree pollen allergens in patients with BP allergy were compared with those in patients without BP allergy. With all the allergens a significantly higher frequency of positive test results was found in those with BP allergy than in those without. Only very small differences were noted between various parts of the country, and sensitization against various tree pollens was common even in regions where the corresponding trees do not grow. It was concluded that a high degree of cross-sensitization exists among tree pollens, and testing with BP allergen is sufficient for the diagnostic screening of tree pollen allergy.

The distribution of trees and bushes in Sweden (viz. lignoses) of possible allergic importance is presented and comments made on analyses of pollen counts of lignose taxa from different parts of the country. Based on these data, 20 lignose taxa were selected for an allergen panel and used in a multi-centre study covering Sweden with the aim of revealing the pattern of sensitization to these plants among sufferers of springtime hay fever.