Background: Several studies have shown that the prevalence of allergy and allergen sensitization has increased in recent years. However, the changes in the pattern of IgE reactivity to individual allergens are mostly unknown.

Objective: The aim of this preliminary study was to assess the change in IgE reactivity profile to individual timothy grass and/or birch pollen allergens in sera from sensitized individuals randomly collected 20 years apart.

Methods: Serum samples from 51 sensitized individuals were obtained from 2 cross-sectional surveys performed in 1973 and 1994 using random samples from Vammala, Finland. The sera were analyzed for IgE reactivity to timothy grass and/or birch pollen extracts, recombinant (r)Phl p 1, 2, 5, 6, 7, 11, 12, native (n)Phl p 4, and rBet v 1, 2 and 4 by immunoassay (ImmunoCAP).

Results: The median (range) concentrations of IgE antibodies to timothy grass and birch pollen were higher in 1994 than in 1973 (6.47 [0.35 to >100] kUA/L vs 1.53 [0.40–25.3] kUA/L; P = .0035). The prevalence of IgE reactivity to some allergens was higher in 1994 than in 1973, particularly rPhl p 5 (52% vs 19%), rPhl p 6 (43% vs 12 %), and rBet v 1 (100 % vs 29 %). There was a correlation between timothy grass pollen-specific serum IgE
levels and the numbers of IgE reactivities to individual allergens (ρ = 0.76, P < .001).

Conclusions: The increase in specific IgE levels together with a possible increase in the prevalence of IgE reactivity to the major allergens Phl p 5 and Bet v 1 between 1973 and 1994 may have contributed to the increase in atopic conditions in Finland.

Key words: Birch pollen. IgE reactivity. ImmunoCAP. Recombinant allergens. Timothy grass pollen.