I've had that problem!! The flea will suck the life out of the kittens! My pet food place told me about the only one they know of for small critters, even nursing kittens. It works great, and the kittens were fine. Its called " NATURAL CHEMISTRY" brand DE FLEA pet shampoo. I hold them under slowly running warm water, spray it on and rub around. Then rinse. Good luck. Also, if they have fleas, they have worms,too. Need to get them de-wormed. Poor things, but they really to get healthy!!