Why is there no effective alternative to metal salts in antiperspirants?
Which biological and chemical processes underlie the effect of    antiperspirants that make metal salts so effective?


Aluminium-based complexes present in the antiperspirants react with the electrolytes in the sweat to form a gel plug in the duct of the sweat gland. The plugs prevent the gland from excreting liquid and are removed over time by the natural sloughing of the skin.  From a biological point of view, it interact with the keratin fibrils in the sweat ducts and form a physical plug that prevents sweat from reaching the skin’s surface.


Why are aluminium salts used most commonly?


Aluminium salts have a  astringent effect on the pores causing them to contract, further preventing sweat from reaching the surface of the skin. Aluminium salts are also natural antimicrobial agents, so they control bacteria on the skin, reducing unpleasant odors.
Some of the aluminium salts used in antiperspirants:

Aluminium chloride
Aluminium chlorohydrate
Aluminium zirconium tetrachlorohydrex gly (an aluminium-zirconium compound)