With a feral cat in our house, the infamous RP the Cat, our decidedly non-feral cats, Meatball/Mousetrap and Destructo have suffered from fleas.
This has particularly been hard on Destructo, as he is a long hair.
I have tried the normal treatments, Frontline® and Advantage®, but they have been of limited effectiveness, I think that the fleas have developed resistance, and they are rather pricey, and Destructo must have the back of his head shaved (he hates this) for this to work, because otherwise it never makes contact with his skin.
I had heard that brewers yeast ameliorates flea infestations, so twice a week, we take a can of wet cat food, mix in two heaping teaspoons of brewers yeast.
The cats love the wet food, and it works like a dream.
Destructo is now almost completely free of flea sores, and their fur is thicker and more luxurious.
It’s easy, cheap, and it involves no cat induced blood loss.