You can buy alum powder or a block of alum over-the-counter, at a drugstore or at the supermarket. Make sure you buy quality product, as many are not 100% natural alum. Buying 100% natural alum will help you mask the underarm odor better, than those products which are not genuine. Alum is a great alternative to commercially available deodorants, aftershave, and skin whitening creams. Also, if you are traveling, then it makes one of the best traveling underarm care products.