For the prevention of heartworm disease, Revolution must be applied monthly, preferably on the same date each month. Drs. Foster and Smith recommends (and our guarantee requires) that Revolution be used year round, although some veterinarians may recommend using it only during the mosquito season. If used seasonally, the first dose must be applied within 30 days of the pet's first exposure to mosquitoes. The last dose must be applied within 30 days after the pet's last exposure to mosquitoes. To control fleas, apply the first dose one month prior to the expected start of the flea season. Part the hair on the back of the pet at the base of the neck in front of the shoulder blades. Place the tip of the tube on the skin and squeeze the tube 3-4 times to empty the entire contents on the skin. Do not massage into skin or apply to broken skin. Do not apply when the haircoat is wet.