EGT / L-Ergothioneine / Longevity Vitamin
A sulphur-containing amino acid the body can't synthesise — it's taken up from diet (mushrooms are by far the richest source) through a dedicated transporter, OCTN1, that concentrates it in tissues under oxidative stress. In skin it behaves as a stable antioxidant and cytoprotectant: it scavenges reactive oxygen species and supports mitochondrial resilience. That dedicated transporter is part of why researchers describe it as a possible 'longevity vitamin' rather than a generic free-radical sponge.
Topical formulas typically use ergothioneine between 0.1% and 2%, straddling the 1% line. Because it's stable and water-soluble, it's usually paired with vitamin C, vitamin E or niacinamide rather than used alone — antioxidants work best as a network. As with any antioxidant, air- and light-tight packaging matters as much as the headline number.
Topical 0.1–2%, AM and/or PM, layered under moisturiser. It's non-irritating and well tolerated, so it suits sensitive and reactive skin. Most useful as part of an antioxidant network — alongside vitamin C and E, and under daily SPF.
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