Disclosed is a composition for controlling parasites on animals, which comprises an N-arylpyrazole (such as fipronil or 5-amino-4-trifluoromethylsulphinyl-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-thiocarbamoylpyrazole) and a pyrethroid (such as flumethrin or permethrin) in a formulation comprising: an aliphatic cyclic carbonate selected from ethylene carbonate or propylene carbonate and mixtures thereof an aliphatic cyclic or acyclic polyether being an ether derived from a diol having up to 8 carbon atoms (such as diethylene glycol monoethyl ether, diethylene glycol monopropyl ether or dipropylene glycol monopropyl ether), or a 5- or 6-membered cyclic ether having a ring oxygen and 4 or 5 ring carbon atoms and optionally carrying a alkyl substituent (such as tetrahydrofurfuryl alcohol) and one or more esters of a dihydric or trihydric alcohol having up to three carbon atoms with organic fatty acids having 6 to 18 carbon atoms.
