i use this for my dogs. we live in the country, so we are prone to fleas. this works the best out of everything i have ever tried. within 3 days fleas were gone. i tried so many powders collars sprays, drops, natural and not this is the best my vet said the chemicals are not even as bad as ones found in other brands like hartz, which i will never use on my animals again due to personal experiences where my cat had a seizure and my mother in laws dog was twitching after as well .