The present invention relates to a liquid pest control system that includes a synthetic pyrethroid as a pest control active ingredient and an agent selected from the group consisting of purified diethylene glycol monoethyl ether, tocopherol nicotinate and tocopherol succinate, and combinations thereof, to reduce or eliminate paraesthesia of the synthetic pyrethroid. The system releases the synthetic pyrethroid efficiently and uniformly. The pest control system is less irritating to the animal's skin as compared to prior art systems, particularly to the small breeds of dogs. The system is useful for making liquid spot-on treatments, sprays and the like.