Some beauty salons provide hair refutation service (some short-haired women want to grow long hair at once), that is, hair made of bought hair has many uses, such as making wigs. If it is used in the right direction, it should be a good thing, but if it is used as soy sauce, it will be terrible. Experts explained that this mainly refers to chemically synthesized soy sauce, because the hair is rich in protein. After simple acid hydrolysis, a certain amount of protein can be extracted and made into "crude water". A few years ago, in order to make the contents of amino acids and protein in soy sauce reach the standard, an underground black factory used this "hairy water" to prepare chemically synthesized soy sauce, which was once exposed by CCTV, because modern people's chemicals for washing hair, perming hair and dyeing hair will remain on their hair. Hair contains arsenic, lead, etc. People who eat this soy sauce will increase the content of arsenic and lead in their bodies, which is not good for their health. Of course, not all chemically synthesized soy sauce is made of hair. Qualified synthetic soy sauce is made from protein extracted from plants.