A sulfonic acid derived from the amino acid cysteine, listed as a skin-conditioning ingredient.
What it is
Cysteic acid is L-3-sulfoalanine, an amino acid formed by oxidation of the thiol group of cysteine to a sulfonic acid group; it occurs, for example, in oxidised hair keratin. CosIng lists it as a skin-conditioning agent.
Where it is used
Appears on the ingredient lists of a small number of 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.
Functions
- Skin conditioning
- Maintaining the skin in good condition.
EU regulation
This ingredient is not listed in the annexes of Regulation (EC) No 1223/2009 in the CosIng data.