My Sister-in-Law works for a Veterinary Clinic/Animal Hospital/Rescue place and gave me this tip when I mentioned that I had been attacked by a dog on my daily walk but fortunately the owner came out and sent it back in his yard before it could do any harm. They use this system when training dogs and all they do is use an aerosol spray (any will do, air freshener, deodorant spray, etc). They are totally harmless to the dog but the dogs do NOT like them and will immediately turn tail and take off. I carry one with me at all times and if I see a loose dog and feel threatened I have it ready and just a small spray in their general direction and they are off. Try it if you don't believe me - for those of you who have a cat or dog in the house now you know why they run like hell when your girl is spraying her hair or you are using a spray deodorant.