I am asking about a substance called L-cysteine used as a small additive in bakery products (less than 1-2%). L-cysteine is an amino acid and its main source is from human hair. Human hair is decomposed by using an acid to L-cysteine. Is this Halaal since it is found in most of bread and other bakery products?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If the product in question is abstracted from human hair as mentioned in the question, then it is forbidden, because using human hair is unlawful. Al-Bahooty says in Sharh Al-Muntahe (a Hambali Book) 'It is forbidden to use human hair.'

Ibn Nujaym  said in Al-Bahr Al-Raiq (a Hanafi Book) while talking about the human being's tooth: 'It is forbidden to benefit from it, out of respect to the human being himself. The same rule applies to the eating wheat that is ground with a human being's tooth as it is unlawful to eat the bread made of its flour, not because of its impurity, but rather to honor human beings.'

An-Nawawi said in Al-Majmoo' (As-Shaafi'ee Book) 'It is forbidden to benefit from the human hair and all his other parts for his dignity, instead his hair should be buried.'

So, we believe the product you asked about is unlawful and it is also unlawful to eat bread that contains any of this product.