Formaldehyde Replacement with Glyoxylic Acid in Semipermanent Hair Straightening: A New and Multidisciplinary Investigation

The study investigated the use of glyoxylic acid as a safer alternative to formaldehyde for semipermanent hair straightening. Researchers examined the interactions between hair keratin and straightening agents using Raman and IR analyses on yak hair and SEM analyses on yak and curly human hair. The results showed that glyoxylic acid caused significant conformational changes within the hair fiber, particularly affecting the secondary structure and disulphide bridges, and led to the formation of imines. The study concluded that the electrophilicity of the carbonyl group and temperature are crucial for the straightening process, with SEM analyses confirming the treatment's effectiveness at the cuticular level.