The ethanolamine salt of thioglycolic acid, used in depilatories and perms and regulated in Annex III.
What it is
Ethanolamine thioglycolate is (2-hydroxyethyl)ammonium mercaptoacetate, the monoethanolamine salt of thioglycolic acid, a reducing agent that breaks the disulfide bonds of keratin. CosIng lists it as a depilatory, hair-waving or straightening and reducing ingredient. In the EU it is covered by Annex III (substances subject to restrictions), both by the entry for thioglycolic acid and its salts, with mandatory label warnings, and by the entry for monoalkylamines, monoalkanolamines and their salts.
Where it is used
Found in depilatories and hair waving or straightening products.
Limits of interpretation
The INCI list shows which ingredients are present, not how much of each. Above 1%, ingredients are listed in descending order of weight; below 1% the order is free.
See the EU regulation section for the applicable limits, conditions and label warnings, which depend on the product type.
Functions
- Depilatory
- Breaking down the the mechanical strength of hair fibers so that they can be removed by mild scraping/rubbing.
- Hair waving or straightening
- Modifying the chemical structure of the hair, allowing it to be set in the style required (permanent waves or hair straightening).
- Reducing
- Changing the chemical nature of another ingredient by adding hydrogen (or removing oxygen).
EU regulation
- Maximum concentration
- Maximum secondary amine content: 0.5%
- As of
- 3 November 2026 · (EC) 2009/1223
- Product type
- (a) Hair products (b) Depilatories (c) Hair rinse-off products (d) Products intended for eyelash waving
- Maximum concentration
- (a) (i) 8% (ii) 11% (b) 5% (c) 2% (d) 11% The abovementioned percentages are calculated as thioglycollic acid
- Conditions and warnings
- Conditions of use: (a) (b) (c) (d) Avoid contact with eyes Rinse eyes immediately if product comes into contact with them. (a) (c) (d) Wear suitable gloves Warnings to be printed on the label: (a)(i) (b) (c) Contains thioglycolate Follow the instructions Keep out of reach of children (a)(ii) (d) For professional use only Contains thioglycolate Follow the instructions’
- As of
- 3 November 2026 · (EU) 2015/1190