Since the increasing exposure we have to chemicals may be a causative factor in health problems I prefer to reduce exposure when possible. I use the spray on for that reason.
Do I know there is a any real concern here? No, but I prefer to be cautious in regard to my health. Except of course when it comes to hiking alone, hiking at night, climbing up steep places, going out it blizzards, going out in bear & mountain lion country, etc. :)