Sentinel is actually a very safe product for collies. It is the intercepter base with an added flea egg/larve control. If you have a flea problem i would recc. to be on sentinel with a topical flea control like frontline. If you dont have a live flea problem or a tick problem then you really only need the sentinel. Sentinel has been on the market for over 10 years and is very safe. Just a note if you use sentinel. Be sure to give it with a meal so it is absorbed properly.