K9 Advantix II kills fleas, ticks and mosquitoes through contact. No biting required. These parasites can be more than just a nuisance. They can also cause potentially serious health risks: Ticks can transmit diseases, such as Lyme disease and Rocky Mountain Spotted Fever, when they bite your dog. Flea bites can cause flea allergy dermatitis (FAD), an allergic reaction that can lead to constant scratching, severe itching and hair loss. If swallowed, an infected flea can also transmit tapeworms, one of the most common parasites. Mosquitoes can transmit deadly diseases. K9 Advantix II also repels biting flies and kills lice. For use on Extra Large Dog (Over 55 Lbs).