Effipro spray for dogs and cats contains fipronil. Fipronil is the most widely used active ingredient in the world to control fleas and ticks in pets. Fipronil combines a good effect against fleas and ticks with a high safety profile for dogs and cats. The spray works for cats for up to 6 weeks and against ticks for up to 4 weeks. Dogs are protected from fleas for up to 3 months and from ticks for up to 4 weeks. Effipro Spray must not be used with: young puppies and kittens, pets other than dogs and cats, sick and convalescent animals, with hypersensitivity.