Fleas....

We have something here called Program (there are other brand names as well). You apply a drop to the back of the cat's neck once a month and any fleas which jump on the cat get a little dose (I gather that it stays in the cat's fatty tissue) and become sterile. As fleas don't have a very long life cycle, it won't be long before there are no fleas on the cat or in the house. It works for dogs, too, and, since I have used it, I've never had any problem with fleas whatsoever.

Visited the vet and got some prescription stuff. Nothing else ever worked.