Promotion of Hair Growth by Applying Sulfur Amino Acids and Other Compounds to the Skin

The study found that applying L-methionine and L-serine to the skin was most effective in promoting hair growth, followed by acetyl L-methionine and L-serine. Glutathione application, however, inhibited hair growth. Direct application of L-cysteine was effective but less so than L-methionine and L-serine. Adding inosine to L-methionine and L-serine resulted in thicker and longer hair roots. There was a proportional relationship between hair weight and root length. Acetyl L-methionine solution did not produce a bad odor or decompose after being stored at 37°C for 15 weeks.