Re Vicks on the feet..
There are no mystical ingredients that get magically absorbed by your feet. Don't forget, you have skin on your chest too, if there was going to be any "magical absorption" it would be absorbed just as well on your chest as your feet.
It works because of the vapour. It's Vicks VAPOUR Rub.
The only reason for putting it on feet instead of chest is for babies/very young children so that the vapour is not as overwhelming. Feet are further away than chest.