Fundamentally, for contact dermatitis due to hair dye allergy is ultimately related to individual differences, meaning that it only occurs in people with allergic qualities. As long as there is a public demand for hair dyeing, there will be hair dyeing dermatitis. What we can do is try to reduce the occurrence of hair dye dermatitis by something regulatory, but we can’t eliminate it. The main ingredient in hair dye products, p-phenylenediamine, is basically composed of a benzene ring, an amine group and a nitro group. Since p-phenylenediamine is a strong allergenic substance, it is the focus of all scientific research efforts. According to current domestic and international literature, all hair dyes for hair coloring purposes contain such ingredients, and pure natural products do not exist. In this regard, consumers need to shine their eyes, and manufacturers need to be careful when advertising. However, the impurities in the hair dye solution is also an important cause of hair dye allergies. Take DuPont’s product p-phenylenediamines (p-Phenylenediamines, PPD) as an example, used for cosmetic purposes (PPD)
Cosmetic
Grade) and industrial purposes are different, but the effect of hair dyeing is the same. This means that inferior products can also dye hair, but increase the chance of allergy and poisoning for consumers. In response, the Ministry of Health of the People’s Republic of China has developed the “Hair Dye Raw Material List (Trial)” to regulate the quality of raw materials for hair dye products and to maximize the safety of dyes. At the same time, the regular manufacturer should have the approval number of the Ministry of Health of the People’s Republic of China for special purpose cosmetics. Consumers are advised to ask for a copy of the approval when purchasing the product. In addition to being allergenic, another hazard to benzene is the tendency to induce tumors. Therefore, hair dyeing is as harmful to health as smoking. From a doctor’s point of view, we do not encourage hair dyeing. According to reliable domestic and foreign literature, the population incidence of allergic diseases is higher in white than yellow people. However, regarding the statistics of hair dyeing dermatitis, the incidence of hair dyeing dermatitis in Thailand and China is much higher than that in Europe and the United States, which suggests that there are problems with the quality of products and methods of use. The increase of poor quality products in the domestic market and the lack of skin testing before use are probably the most important reasons. In addition, home hair dyeing increases the chance of skin contact, which can also lead to a higher incidence of hair dyeing dermatitis. Therefore, doctors recommend that a sensitivity skin test should be done 48 hours in advance of hair coloring. Those with positive results should not dye their hair. For those consumers who have a history of hair dyeing allergies, once a positive p-phenylenediamine patch test is determined, it is recommended that they never dye their hair again for the rest of their lives. For consumers with a negative skin sensitivity test, an important principle for hair coloring is to use a qualified product, but to avoid skin contact as much as possible.