Abstract Allergies caused by pollens affect 10 to 15% of the general population. A pilot study was carried out in Clermont-Ferrand (France) over 2000-2001 to analyse the short-term relationship between the daily variations in rhinitis and/or allergic conjunctivitis and the daily variation in pollen counts in the ambient air. ERASME data (French National Health datawarehouse) made it possible to identify all the subjects to whom at least one drug was prescribed to treat a rhinitis or an allergic conjunctivitis. One case of allergic rhino-conjunctivitis (ARC) was defined according to the following criteria: i) was domiciled in the study area, ii) was 5 years old or over and iii) had on a given day, a prescription for an oral antihistamine associated with a local treatment for allergic rhinitis, for allergic conjunctivitis, or for both. Ten allergenic pollens and a pollen control were studied. A Poisson regression model using penalized Spline functions was used. A positive and significant association was found for pollens of Betula, Cupressaceae, Quercus, Fraxinus and Poaceae. The relative risks varied between 1.3 (IC95 % :1.0-1.5) and 1.2 (IC95 % :1.1- 1.5) for an interquartile range increase of daily pollen counts of Cupressaceae (13 grains/m3) and of Betula (45 grains/m3) respectively. Further analyses are necessary to confirm these results, in particular using longer time series of pollen and drug prescription.