PLEASE CHECK THE LABEL FOR AGE! Jen is right, some are not safe for 'kittens'....

Second, I would vaccuum and wash everything you can...then powder everything. I had ONE really really bad flea infestation. It was probably infested before I moved in. The twins were just babies, maybe 3 months at the time. I had a professional company come and treat the house and the yard, then I bathed everyone..not fun- bathing five cats.

Good luck and be persistant.