Veterinary Formula Flea and Tick Spray for Dogs provides dogs with up to 14 weeks of protection against fleas and ticks – the longest lasting results available on the market today. Also prevents re-infestation and the development of flea larvae and eggs. Fleas and ticks can cause undue skin irritation and can even infect your dog with disease. This unique spray uses the natural insecticide, pyrethrum to kill fleas and ticks on contact. Veterinary Formula Flea and Tick Spray for Dogs also includes Nylar to prevent the development of flea larvae and eggs and permethrin to give long-lasting protection against adult fleas to prevent re-infestation.