Disclosed is a composition for killing ectoparasites and/or their eggs, comprising at least one volatile, at room temperature liquid, non-polar organic solvent, 1 to 10 wt.-%, based on the total composition, of at least one spreading agent and 35 to 65 wt.-%, based on the total composition, of at least one polysiloxane having a viscosity of greater than 90 cSt.