I use Revolution on mine and also a topical natural spray in mine.
Ark Naturals
Ark Naturals :: Flea & Tick. I prefer the protect one because Buddy is allergic to both fleas and ticks. Thankfully in my area only ticks are a problem.
Boric acid can be used safety on all fabrics and even in his bedding. You should be able to buy it at most grocery stores or the pharmacy.