What are the roles of glyoxylic acid and glycolic acid in hair?

Glyoxylic acid (GA) is a straightening agent for hair care products. It produces a semi-permanent straightening effect without destroying the cystine disulfide bridge. It has a long-lasting relaxing effect on the hair fibre without causing damage to the hair or irritating the scalp as alkaline chemicals and other hair straighteners do. The carboxyl and aldehyde groups of Glyoxalic Acid react with the amine groups in hair keratin to form stable bonds.

Glyoxalic Acid 50H is used in straightening formulations to soften wavy and tight curls. When used in flat irons, it softens natural curls, gives hair a silky shine and improves manageability.

However, due to the continued use of Glyoxylic acid products can produce odour and discolouration. Glycolic acid (GCA), on the other hand, acts as a GA penetration enhancer and helps to minimise the concentration of GA for more comfortable use.

References:

[1] MAKOTO UYAMA. Promotion of glyoxylic acid penetration into human hair by glycolic acid[J]. International Journal of Cosmetic Science, 2023. DOI:10.1111/ics.12838.