Phenylthioglycolic Acid
INCI: PHENYLTHIOGLYCOLIC ACID
Reviewed by Daisy · Last updated 14 Aug 2026
Also known as: Phenylthioglycolic Acid
A sulphur-containing antioxidant that helps protect skin from oxidative stress
Best For Skin Types
All, Mature, Sensitive
Addresses
Usage Frequency
Daily
What Is Phenylthioglycolic Acid?
Phenylthioglycolic acid is a naturally occurring amino acid derivative containing sulphur. It functions primarily as an antioxidant in skincare formulations, working to neutralise free radicals that can damage skin cells and contribute to visible signs of ageing.
This ingredient is less commonly used than mainstream antioxidants such as vitamin C or niacinamide, but it appears in a modest range of skincare products, often in combination with other protective compounds.
Benefits for Your Skin
How It Works
Phenylthioglycolic acid works by donating electrons to unstable free radical molecules, rendering them harmless. This antioxidant mechanism reduces oxidative stress within the skin, which can slow the accumulation of cellular damage linked to premature ageing.
The sulphur component of the molecule may also contribute to skin's natural defence systems, though the extent of this benefit in topical formulations requires further investigation.
Clinical Evidence & References
Evidence specifically on phenylthioglycolic acid in skincare is limited. Most data comes from biochemical studies rather than robust clinical trials on human skin. The ingredient's antioxidant capacity is well-established in chemistry, but its real-world efficacy compared to better-studied alternatives like vitamin E or resveratrol has not been extensively documented.
It is generally assumed to be safe and supportive within antioxidant formulations, but consumers should not expect transformative results from this ingredient alone.
How to Use
Phenylthioglycolic acid is typically used as part of a broader antioxidant or anti-ageing formula rather than as a standalone treatment. Apply as directed on the product label, usually once or twice daily. It works best as part of a consistent routine that includes sunscreen, as antioxidants are most effective when paired with UV protection.
Safety & Precautions
Frequently Asked Questions
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