Very few studies have investigated the seasonal aspect of grass pollen sensitisation or its evolution in the allergic canine population. The aim of this study was to evaluate both these aspects. A study of canine grass pollen sensitisation was performed throughout the statistical analysis of 261 intradermal skin testings (IDT=25 allergens tested on average) performed from January 1999 to December 2010. IDTs were performed on dogs with pruritic allergic skin disease. χ(2) Tests were used for statistical analysis. Two hundred and thirteen dogs (81.6 per cent) were sensitised to at least one allergen, and 56 (21.5 per cent) to at least one grass pollen. No increase in the rate of positive IDT was recorded over three periods: 1999-2002, 2003-2006 and 2007-2010. No statistical correlation was detected between sex, age or birth month and grass sensitisation. Moreover, no link was found between the season in which the IDT was performed and sensitisation, indicating that there is no seasonality to the sensitisation. However, considering the grasses tested over these three periods (grass mix and rye grass), a clear and significant increase in the percentage of dogs sensitised to grass pollen was observed between 1999-2002 and 2007-2010 (14.4 per cent and 27.7 per cent, respectively). The possible reasons for this sensitisation increase of dogs to grass pollen are discussed.