Objective: The aim of this study was to evaluate the relative frequencies of sensitisation to four common inhalant allergens in two atopic populations suffering from asthma and/or rhinitis. One had been studied in the period of 1975 till 1979, and a second population was evaluated between 1992 and 1995.
Data sources: At both time periods patients with inhalant allergy and visiting our outpatient clinic were included. Quantification of IgE to Dermatophagoides pteronyssinus, birch, timothy grass, and mugwort was performed via the Phadebas RAST technique (Pharmacia, Brussels, Belgium).
Results: In patients suffering from respiratory allergy the frequency of birch pollen sensitisation significantly increased from 13% in the period 1975-1979 to 34% in the period 1992-1995. In contrast, the frequency of house dust mite, timothy grass pollen, and mugwort pollen sensitisation remained almost unchanged. The increase was not associated with an increase in the birch pollen count.
Conclusion: Birch pollen hypersensitivity has almost tripled among atopic subjects during the last 2 decades. The exact mechanisms for this increase remain to be evaluated.