Hair dye can turn the gray hair on people’s heads black and improve their image, so many people with gray hair like to dye their hair, hoping to make themselves look younger and more beautiful. However, new scientific research proves that chemical hair dyes do not only “paint” the surface of the hair black, but they are also absorbed by the hair into the cortical layer, and eventually enter the skin through the cortical layer, which is harmful to the human body. Moreover, chemical hair dyes inevitably reach the scalp and are absorbed directly into the hair follicles and cortex. And too frequent hair coloring can bring serious health hazards. There is a chemical substance called “phenylenediamine” in traditional hair dye, which is used in the process of hair dyeing to open the hair scales on the surface of the hair through a chemical reaction, allowing the dye to enter the hair to achieve the purpose of coloring. Because “phenylenediamine” is called “coloring agent” by pesticide manufacturers, its disadvantage is that not only does it take a long time to color, at least one and a half hours per dyeing, but also “phenylenediamine” is a toxic substance that goes down the hair. It is a toxic substance that enters the body along the hair roots and becomes a major cause of human disease and a direct health hazard. Traditional hair dyes use bleaching and dyeing technology to dye hair, bleaching and dyeing means that the hair scales are opened by chemicals and so on, so that the dyeing substance enters the hair and achieves the purpose of dyeing. People who dye their hair often open the hair scales, and the hair quality is often damaged. In addition, when the hair scales are opened, some chemical substances such as phenylenediamine, benzophenol, lead and mercury enter the hair, which damages the hair and destroys the natural growth environment of the hair, and causes a large loss of nutrients in the hair. The hair coloring cosmetics that occupy 70%-80% of the total market share have been oxidizing hair dyes with aniline compounds as the main body and benzylamine, paraoxyphenol and p-toluenediamine compounds as the auxiliary. Among them, p-toluenediamine has a small molecular weight and easily penetrates into the hair pith, causing skin allergy, redness, rash, water scars, pain and itching, and often induces asthma, anemia and many other diseases when dyeing hair allergy. A few inorganic hair dyes such as lead salt and silver salt hair dyes contain heavy metal ions, which are more harmful to the human body, and once they enter the human organism, they will be difficult to metabolize and excrete, which will easily cause accumulation of poisoning and incur some diseases that are difficult to treat. Among the hair dyes, the most controversial is the carcinogenicity.