Charleen said:...I always give the dogs and cats Advantage or Frontline, but this year my vet told me to use Sentinel because it combined the heartworm treatment with flea repellent. That sounded good for my dogs, so I said yes. When I saw the flea on Saturday, I went to the Sentinel website and found out that it doesn't cover all stages of flea life and doesn't kill adult fleas. So just 2 days ago, I applied Frontline Top Spot to kill those nasty fleas. My own cat is allergic to flea bites, so all fleas must die!