Potassium Alum
Potassium alum
- Role
- A mineral potassium-aluminum salt used in deodorants as an astringent ingredient.
- Catalog formulas
- 3
- Type
- Odor
- Verified
- 06.11.2026
What does this ingredient do in an antiperspirant?
Chemically it is aluminum potassium sulfate. CosIng assigns it the functions "astringent" (tightens the skin) and "antiperspirant".
Part of a system, not a label in isolation
It is found in "crystal" deodorants and products positioned as natural, including water-based roll-ons. When a formula contains no FDA-recognized aluminum salt, it is more accurate to assess it as a deodorant.
Potassium alum is not on the FDA M019 list of antiperspirant actives, so in the US it is not a recognized active for over-the-counter antiperspirants. As an aluminum compound, it falls under the general SCCS assessment of aluminum in cosmetics (SCCS/1662/23).
The astringent effect may be felt on freshly shaved or damaged skin. The cited sources contain no specific clinical data on irritation from alum.
"Mineral" or "natural" does not mean "aluminum-free": alum contains aluminum. At the same time, it is not Aluminum Chlorohydrate or Aluminum Chloride, the FDA-recognized actives that reduce sweating.
Products containing Potassium Alum
Links are based on the complete published INCI list for the exact product version.
Sources
The conclusions apply to the stated conditions and jurisdictions, not automatically to every concentration or product.
- COSMILE Europe (CosIng data): Potassium Alum Supports: function
- FDA OTC Monograph M019 Supports: list of active ingredients
- PubChem: Aluminum potassium sulfate Supports: substance identity
- SCCS/1662/23: safety of aluminum in cosmetic products Supports: safety assessment