Core Viewpoint - The article discusses the health risks associated with hair dyeing, highlighting the presence of harmful chemicals and the potential for allergic reactions and other health issues related to frequent use of hair dye products [1][3][5]. Group 1: Health Risks of Hair Dye - Hair dyes commonly contain a chemical called para-phenylenediamine, which increases the burden on the kidneys as it needs to be excreted [1]. - Heavy metals such as lead, iron, copper, and mercury found in hair dyes can be absorbed through the scalp and hair, potentially causing kidney damage [3]. - Long-term exposure to certain components in hair dyes, such as aniline, phenol, and hydrogen peroxide, may increase cancer risk, although no definitive conclusions have been established [3][5]. Group 2: Recommendations for Hair Dye Use - It is advised to limit hair dyeing to no more than twice a year and to avoid using expired products [5]. - Users should refrain from mixing different brands of hair dye to prevent chemical reactions that could produce toxic substances [5]. - Individuals with sensitive scalps are recommended to apply a protective layer of petroleum jelly or cream before dyeing to minimize direct contact with the dye [7]. Group 3: Plant-Based Dyes - The term "plant-based dye" can be misleading, as many products still rely on chemical components despite claims of being natural [8][11]. - While plant-based dyes may have lower irritation and allergy risks, they often have limitations in color variety, application difficulty, and color longevity [9]. - Consumers are advised to verify ingredient lists and safety warnings when purchasing hair dye products, especially those marketed as "pure plant" [11].