There are two main differences between Potassium alum (Aluminium potassium sulfate dodecahydrate) and the salts Aluminium chloride and Aluminium chlorohydrate which are commonly used in antiperspirants.
Potassium alum vs Aluminium chloride/chlorohydrate
These last two salts react with peptides and amino acids in the skin to form a gel which then blocks sweat ducts and glands, preventing perspiration.
They also have a small molecular mass (typically between 250-350 Daltons) meaning that they can readily penetrate the skin and cross the skin/blood barrier, thereby entering the body.
Potassium Alum has a much larger molecule (around 480 Daltons) which is too large to be absorbed through the skin (the maximum size that can be absorbed is less than 450 Daltons).
Instead of forming a gel, thereby preventing perspiration, Potassium Alum sits on the surface of the skin where it prevents the bacteria responsible for causing sweaty odours from multiplying.
Potassium alum deodorants by Green People
Safe and gentle on your skin, Green People's natural and organic deodorants keep you feeling fresh without the use of pore-clogging aluminium salts.