29 citations,
August 2005 in “Biopolymers” L-cysteine slows down the breaking of bonds in hair due to electrostatic interactions.
20 citations,
December 2012 in “Journal of molecular structure” The study found that thioglycolic acid breaks down hair bonds more consistently than l-cysteine, which is less damaging to hair.
5 citations,
April 2005 in “Journal of applied polymer science” PEI diffuses into hair at a constant rate, and urea speeds up this process.
7 citations,
January 2001 in “Comprehensive series in photosciences” UV radiation significantly damages hair, especially with humidity, making it more vulnerable to further damage.
5 citations,
October 2003 in “PubMed” Chemical treatments and light exposure damage hair proteins.