Perkin discovered the first aniline intermediate and used it as a hair dye product. Up to now, the main raw materials of almost all brands of hair dye products, including world-famous brands L 'Oreal and Icarus, are still synthetic oxidation dyes with aniline intermediates as the main body. From 194 1 year, mcdonough filed a patent for sulfhydryl cold ironing agent. Today, the main raw material of almost all brands of perm products, including Na Wei, a world-famous brand, is still thioglycolic acid. P-phenylenediamine is a toxic substance, which has strong irritation, allergy and toxic side effects on human body. There are countless health risks caused by allergies and irritation caused by hair dyeing, and the accumulation formed by long-term use is more harmful to the human body, and even causes cancers such as skin cancer, leukemia and bladder cancer. Thioglycolic acid is also very easy to invade the body through the skin, which is very irritating to the skin and mucosa, has a strong destructive effect on the hair surface and is mutagenic.