My cat has extremely sensitive skin (right now we are battling with her over grooming her arm pit....), so chemicals are out of the question. I've found that washing her with hand made basil soap works wonders. I also have a bottle of "Buzz Off" which is a natural bug repellent that she gets two squirts of once per week. The bug repellent contains Joboba Nut Oil, Vitamin E, Esentilal Oils of: Basil, Bay, Cedarwood, Citronella, Clove, Eucalyptus, Geranium, Lavender, Lemongrass, Orange, Peppermint, and Rose. Surprisingly, this stuff doesn't smell too strongly and you can't even tell there is citronella in it. It also rubs in a leaves you feeling smooth instead of greasy or sticky like commercial flea/tick/and bug sprays.
My only word of caution, I've been bathing my cat once per week for the last 8 years (her whole life), so she is accustomed to holding still. She still doesn't like it, but she doesn't fight it. Do not bathe a cat by yourself for the first few times! Your sweet little fluff ball will turn evil trying to get out of the tub!
I can give the website of the place where I bought the soap to anyone who pms me. The website is still under construction, but they have 13 different types of soap. Their store is located in Asheville, NC.
Hope this helps,
Emily