Better check with your vet before you try any of these. Collies and Shelties can be sensitive to certain chemical ingredients - I've used Frontline Plus for many years with good results, and my present sheltie Buttons has a "show coat" - very thick, but so far no sign of fleas or tick. We were in Colorado 2 weeks ago hiking on the trails and I'm sure there were ticks and other critters, but Buttons had no living souvenirs from our trip. Best wishes to you and all the collies.
Rita
Buttons the princess sheltie
Nicky the spoiled Tennessee Walker