Oh yes indeedy!!!! I have a rinse out treatment with this in it and I've found that I have loads of new spikey growth - anyone with fine hair should give it a go - that and biotin shampoo and scalp rub!!!

Here is what an herbal site says about it:

L Cysteine is a non-essential amino acid that is an important component of hair, nails and the keratin of the skin.
L Cysteine stabilizes protein structure and aids in the formation of collagen, thereby promoting healthy skin, hair and nail texture.
It is used in the treatment of respiratory disorders such as chronic bronchitis.
It stimulates white blood cell activity in the immune system to help build resistance to disease.
Faster recovery from surgical operations and burns is another benefit.