🌿What is Alum? Alum bar is a natural crystalline stone of Pottassium Alum. 🌿How does it work as a natural deodorant? Alum works as a natural deodorant by creating an acidic environment in oou armpits, preventing odor causing bacteria to grow. Can also be used as a shaving bar because alum is also antiseptic and antibacterial. 🌿How to use ? Wet your alum block under tap water and gently rub on your underarms. Allow alum to dry completely before wearing clothes.