I use Sentinel, because it doesn't haven't ivermectin in it (Tri-Heart and Heartgard both do and my vet doesn't carry Interceptor). There are certain breeds that have reactions to ivermectin, Collies being one of the most sensitive to it. Some other breeds on the list that shouldn't have ivermectin, Shelties, Aussies, Sheepdogs, Australian Cattle Dogs, etc.

I've used Sentinel for the last 5 years and have seen no fleas whatsoever on the dogs, that's even with takin' them hikin' through the woods and being around many other dogs at training classes, Petsmart, the neighborhood, etc. No worms of any kind either.

Also, I just did a quick price comparison of a years worth of Sentinel vs a years worth of Interceptor and Frontline Plus and you're going to pay about 50% more for Interceptor/Frontline Plus. Since it looks like you have an ACD, I didn't price out Tri-heart or Heartgard.

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