I'd also call the vet before doing anything. I've heard that dawn dish soap also works well and will help kill fleas but I'm not sure about the flea eggs. Good luck.

Both Hatrz and Biospot flea products are very dangerous to use on cats and dogs and I still don't understand why they're still selling these products. I used Hartz flea prevention one time on the 3 cats that I had at the time and luckily no one became ill. Then I saw a post here about how deadly it can be and I threw the rest of it away. I've been using advantage ever since. You have to buy this at the vet, a pet store, or you can buy it online. I'm not sure how old kittens need to be to be able to use this product though. I think at least 8 weeks.