OK, last year, after many successful years on Frontline Plus, my dogs got fleas. It might have been because I was late giving them a dose or because it was just a bad season when the fleas had gotten immune. Anyway, I took them to the vet and he switched them to Comfortis. That worked, along with shampooing the carpet. Now, I saw a tick crawling from the carpet to me foot the other night and I found a tick on one of my dogs tonight. I need to check the other dog to see if she has any. The tick on the one dog was very small so hadn't been there long. I checked the Comfortis package and it only kills fleas. If I switch back to Frontline Plus, will it work now for fleas? Also, I always wondered if Frontline Plus kills ticks after the tick has bitten them, how can it (and does it really) prevent disease spreading?