My dog is allergic to just about every chemical in flea & tick products, so when I had to spend the summer in the country caring for my terminally ill dad, ticks & fleas became a nightmare. Then I discovered one of these repellers in the pet store and tried it. Where my dog would go out for 10 minutes and come back in covered with ticks, he now came back in with no more than one!! And fleas became nonexistent. I don't know what we would do without it!!