NONE OF THEM! Flea and Tick Collars, just like Frontline, Advantage...other commercial LIKE KIND drops and most Flea and Tick shampoos, dips and powders ARE TOXIC. They poison the Fleas, Ticks, Dog, Cat, YOU, your kids, and your friends and other family members! That's what they do and how they work. Check out NEEMS Oil, soap, shampoo products which are great for dissuading Fleas, Ticks, Skeeters, Horse Flys, and other assorted insects. You can usually find Neems oil at Whole Foods, or other health food stores, who will also often order it for you, if they do not carry it. Also, running a Google, you can purchase it on line. If Ticks are especially problematic where you live or as some folks to hunt their dogs and so are exposed a lot to ticks in thick brush do...I would apply one drop to the back of the neck, one to the butt and one to the lower chest area and rub it into the fur...you can use YOUR HANDS, because Neems IS NOT POISON! People who hunt (usually bird-dogs) apply it before each hunt. You can make a spray by adding about 6 drops to the average sized spray bottle of water, I've also seen it in the form of bar soap and shampoo. Our Neighbor was pregnant last summer and her Doctor approved of her using it to keep the pesky skeeters off of her when we would all be outside at night BBQing or sitting in front of our fire ring. It works great with NO poisons!