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Sodium Metabisulfite
Sodium MetabisulfiteAntioxidant
An antioxidant that keeps fragile ingredients from turning brown or losing strength.
What it does
A sulfite salt that protects fragile ingredients, like some active ingredients and dyes, from turning brown or losing strength. It works by reacting with oxygen first, so the other ingredients don’t.
The EU’s ingredient database lists it as an antioxidant (slows reactions with oxygen, like going rancid).European Commission, CosIng (© European Union, CC BY 4.0) · uses put in plain words by Drop ↗
The evidence, graded
expert consensusUS safety reviewers assessed sodium metabisulfite with related sulfite salts (final report published 2003), noting that it works in cosmetics as a reducing agent and an antioxidant. Undiluted, it didn’t irritate rabbit skin, though at 50% it irritated guinea pigs with repeated use. These sulfites may cause reactions in patch tests on people seen by skin doctors. The reviewers judged them safe as used, and confirmed that in 2023.Nair 2003 · International Journal of Toxicology ↗
Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.
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