Does anyone know of herbal or natural flea/tick remedies for (outdoor) cats? Thanks!?

Since my cats are outdoor mainly, and thus exposed to fleas and ticks, this needs to be something that really works! (They also come into our garage and basement--then when they leave, WE get the fleas!!!) I've been using typical flea preventative--Biospot--but I would like to stop using pesticides on my cats.