A pour-on formulation for control of an external parasite on an animal is provided the formulation comprising an effective amount of an ectoparasiticidally active ingredient and at least one C2-C4 dialkylene glycol mono/di - C1-C4 alkyl ether as a carrier. The ectoparasiticidally active ingredient is preferably an insect growth regulator (IGR). There is further provided the use of a C2-C4 dialkylene glycol mono/di - C1-C4 alkyl ether for improving the properties of a pour-on formulation in particular the properties of stability efficacy and water-resistance.
