Be very careful when using chemicals to kill fleas. You can not only kill the fleas, but your dog or cat also. Hartz products sold at Wal-Mart and Sam's club very nearly killed my sister's Jack Russell last spring. He ended up in the ER with an IV. I use Frontline on my 2 dogs and cats and so far it has worked really well. Fleas season seemed to start a lot earlier this year.