Vetoquinol Vi-Fi Forte Spot-On is a topical treatment used for prevention and treatment of fleas, ticks, and chewing lice infestations in dogs. Acts on all stages of the flea life cycle, from eggs to adults, and helps prevent re-infestation. Applied monthly to the dog's skin, at the back of the neck, or between the shoulder blades, enabling the medicine to spread through the dog's skin and hair.