Science
Mechanism of Action
This ingredient functions as a reducing agent, specifically targeting the disulfide bonds found in keratin, the primary protein in hair. By breaking these bonds, it allows hair to be reshaped (for perms or straightening) or chemically dissolved for removal (depilation). On the skin, its reducing properties can also contribute to exfoliation, and it exhibits antioxidant activity by neutralizing free radicals.
Research
Clinical Evidence
High confidence5%
Key findings
- 01 Concentrations up to 5.0% (as Thioglycolic Acid) are considered safe for depilatories when formulated to be non-irritating.
- 02 Reported concentrations in depilatories include 4% (NTP Technical Report).
Transparency
Dusting Analysis
Sodium Thioglycolate is not typically 'dusted' or used in low, broad-application percentages. Its efficacy relies on specific concentrations for targeted actions like depilation or hair treatment, which carry significant safety considerations if not properly formulated and used.
The Formula
Formulation
Stability
Sodium Thioglycolate is hygroscopic and oxidizes upon exposure to air, forming dithiodiglycolic acid; this oxidation rate increases with higher pH and dilution, leading to discoloration (yellowing). It is also incompatible with iron and other metals. For optimal stability, it should be stored in tightly closed, dry, well-ventilated, locked containers under inert gas, protected from light, and ideally at -20 °C, avoiding metal contact.
Conflicts
- metals
- air
- iron
- moisture
Safety
Safety Profile
The Cosmetic Ingredient Review (CIR) Expert Panel deemed Sodium Thioglycolate safe for use in various hair products up to 15.2% (as Thioglycolic Acid), and in depilatories up to 5.0% (as Thioglycolic Acid) when formulated to be non-irritating. However, it is a contact irritant and corrosive substance, capable of causing severe skin burns and eye damage. Hairdressers must avoid skin contact, and consumer exposure should be minimized. While direct sensitization data for sodium thioglycolate is limited, its structural analogue, ammonium thioglycolate, is a known sensitizer.
Your Skin
Skin Compatibility
Our Assessment
Verdict
While effective as a depilatory and hair restructuring agent at specific concentrations, Sodium Thioglycolate's high irritancy and corrosive nature necessitate cautious formulation and use, making it generally questionable for broad application in precision skincare.
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References
Sources