What it is
Potassium Alum is a naturally occurring or synthetically prepared double sulfate of potassium and aluminum. In cosmetics it is valued as an astringent, giving a tightening sensation to the skin, and it is a traditional ingredient in deodorant and aftershave products. In sun care formulas it is used at low levels as a conditioning or astringent additive.
Safety & warnings
Potassium alum is generally well tolerated at cosmetic levels. Its astringent action can feel drying or tightening, and individuals with very sensitive or compromised skin may find it irritating.
Origin & sourcing
Mineral. It occurs as a naturally mined salt and is also produced synthetically; both forms are the same potassium aluminum sulfate compound.
History
Alum has a long history of use dating back to antiquity for purposes such as water clarification, dyeing, and as a styptic and skin astringent, and it continues to be used in personal-care products today.
Questions everyone asks
What is alum used for in cosmetics?
It acts as an astringent that gives a tightening feel and is a classic ingredient in deodorants and aftershaves; in sunscreen it is a minor conditioning additive.
Is potassium alum natural?
It can be mined as a natural mineral salt or made synthetically; both yield the same potassium aluminum sulfate.