External parasites like fleas, ticks, and mosquitos can make your pets life miserable and can carry disease. My preference is to use flea drops from companies like Zodiac and Infestop. They work quickly and keep on working for up to a month. Just make sure you get the drops right down to the skin when applying. For fleas around the home I prefer the 1-2 punch of a fast acting less expensive insecticide using pyrethrins in main areas along with a residual insecticide for cracks and crevices, under furniture etc. where fleas like to hide. Nothing can replace vacuuming for ridding a home of fleas.