I don't want to "poison" my cats but they have fleas. Do any "organic" or non-poison treatments work?

I go through this every year when the weather warms up and all the flea eggs start hatching. I have used Frontline and Advantage but keep hearing how bad it is, causing cancer, damaging livers and quite frankly the cats seem sick for a few days after I put this stuff on them but it does indeed kill the fleas. I tried one brand of "organic" flea treatment last year (can't remember the name) and it actually seemed to make the problem worse. The fleas liked it. One brand has been recommended here - Target Feline Spray - but there are only two reviews for it on line and neither mention if the stuff kills fleas, they just talk about how the cats liked it. Pfft! Has anyone out there used this stuff who can give an unbiased review? Any alternatives? And yes, I know about using a flea comb and flea baths - try giving MY cats a bath!