What it is
Sodium thiosulfate is a water-soluble salt with mild reducing properties that help it scavenge oxygen and stabilize oxidation-sensitive components. In skincare it is used at low levels to support antioxidant systems and to help control unwanted reactions involving trace metals. It contributes to product stability rather than acting as a primary skin active.
Safety & warnings
Sodium thiosulfate is generally well tolerated on skin at the low levels used in cosmetics and is not associated with comedogenicity. As with many salts, very high concentrations could be mildly irritating, but typical cosmetic use levels are low.
Origin & sourcing
A synthetic inorganic salt produced industrially; both anhydrous and pentahydrate forms are used.
Questions everyone asks
What role does it play in a formula?
It serves as an antioxidant and reducing agent and can help stabilize the product by limiting oxidation reactions; it is not a UV filter.
Is it the same as the sulfur sometimes used for blemishes?
No. Sodium thiosulfate is a distinct sulfur-containing salt used here for its stabilizing and antioxidant properties, not as a blemish active.