Flea and Tick Collars do work somewhat at preventing further infestations of Fleas and Ticks on your dog.
But if your dog has Ticks and Fleas you need get the dog dipped in a Flea and Tick bath or treat the dog for Ticks and fleas another way first before using a Flea and Tick Collar.
I use a Flea and Tick Collar on my dog and it does work to prevent further Ticks and Fleas but I do sometimes have to have the dog dipped in a Flea and Tick bath and sometimes use tweezers to remove some ticks that are on the dog.