Abstract: The present invention relates to a hygienic and/or cosmetic and/or disinfectant composition including, at least one repulsive and/or repellent vermin-killer agent. According to the invention, the repulsive and/or repellent agent is a fatty acid. The present invention also relates to the use of the composition as a vermin-killer and/or repulsive and/or repellent treatment composition for arthropods, in particular insects such as flies, when treating and/or washing the udders and/or the dug of mammals.