The Natural Un-odorant in a Foot Spray. Our Crystal Foot Deodorant Spray does a remarkable job controlling foot odor and athletes foot. Small enough to stick in a gym bag. May be used safely by more than one person. Mineral salts are present in the water we drink, in almost all the foods we eat, and in the air we breathe. In its natural form, alum is the third most abundant element in nature, after oxygen and silicon. It has been part of our environment since the beginning of time and is one of the basic building blocks of our universe. Deodorants made of alum based mineral salts feature physically large potassium or ammonium alum molecules which are not absorbed through the skin into the bloodstream.