I have gave a few bears the spray and I have never seen anything run away as fast as they did. where I live the only defense against bears other than bear sprayis the rifle,shotgun or bow you are hunting with when I hunt bears with my bow I carry a can of spray and have used it on a few, and as far as I can tell it doesn't just scare them away it hurts them. It does more than just make their eyes water.A test that you could do is take a bottle of tabasco sauce or your favorite hotsauce will do, fill a seringe(sp?) and shoot it up your nose and suck up at the same time then multiply that by a 100 times. The only time spray won't work on a bear is when you surprise one and you do not have time to get it off your belt but then again good luck getting any sidearm out of its holster in time as well. Good luck in the woods and be safe.