BUTYROLACTONETHIOL is graded A (Safe) by Expert·ING, based on COSING regulatory data.

BUTYROLACTONETHIOL

Safety grade: A

This is a synthetic chemical compound that acts as a reducing agent, meaning it helps break down and relax the protein structures in hair. It's used in hair straightening and waving treatments to reshape the hair's natural structure.

Butyrolactonethiol works as a reducing agent in hair permanent waves and straightening treatments, breaking disulfide bonds in hair proteins to allow the hair to be reshaped into the desired wave pattern or straight style.

Graded using: COSING.

Last verified: May 26, 2026