Does anyone here give this to their cats?

Tigsy and Timmy are off to the vets tomorrow and I know that they will be treated with flea stuff but I am nott 100% sure about putting chemicals on their little bodies.

A friend used to give her cat a brewers yeast tablet everyday for the prevention of fleas, and amazingly even though the cat was a farmish cat he never got flease

So I am thinking once the kitty cats have been flea treated at the vets can I then give them brewers yeast to prevent any further outbreaks? Also the kittens are purely house cats so I am assuming that once the fleas are gone they shouldn't return.

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