I have 2 feamale cats one of which has 4 kittens 8 weeks old, I can't control the fleas, I used frontline on the 2 adults when kittens were 3 weeks old as advised by vet, I then used revolution on kittens at 6 weeks old and frontline again on the adults, they still have major flea problems, as I couldn't aford to do this again I got spot on for all at the supermarket 2 days ago and it seems worse, all the time I am vacuuming and washing floors, I'm very frustrated and want to find homes for the kittens but don't feel right giving them away with fleas... what to do next?

Have they been to the vets for their first shots yet?