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].

Core Viewpoint - The article discusses the health risks associated with frequent hair dyeing, particularly the potential link to kidney diseases, as highlighted by a recent case of a young girl diagnosed with purpura nephritis after frequent dyeing [1] Group 1: Health Risks of Hair Dyeing - Frequent hair dyeing can lead to kidney disease due to the presence of para-phenylenediamine, a common chemical in hair dyes that can enter the bloodstream through the scalp [2] - The kidneys, responsible for detoxifying the body, may become overburdened when high levels of para-phenylenediamine and its metabolites are present, potentially leading to inflammation and impaired kidney function [2] - Some hair dyes may contain heavy metals like lead, which can also harm the kidneys when absorbed during the dyeing process [2] Group 2: Allergic Reactions and Other Health Issues - Users may experience allergic reactions such as scalp redness, itching, and even severe reactions like swelling and blisters, regardless of whether the dye is natural or chemical [3] - Frequent use of hair dyes can damage hair and scalp, leading to dryness, brittleness, and increased risk of hair breakage [3] - Certain hair dyes may release volatile organic compounds that can irritate the respiratory system, causing symptoms like throat irritation and coughing [3] Group 3: Recommendations for Safer Hair Dyeing - To minimize health risks, it is recommended to limit hair dyeing to no more than four times a year and to avoid simultaneous dyeing and perming [4] - Consumers should avoid "three-no" products and be cautious of marketing claims regarding "natural" or "plant-based" dyes, as they may still contain harmful chemicals [4] - Conducting a patch test before dyeing is essential to identify potential allergic reactions [4] Group 4: Precautions and Alternatives - When applying hair dye, it is advisable to avoid direct contact with the scalp and to use protective barriers like lotion or petroleum jelly [5] - Post-dyeing care should include thorough rinsing to remove any residue and using restorative hair products [5] - Individuals with a history of allergies, skin conditions, or compromised health should consult a doctor before dyeing their hair and consider using temporary dyes or wigs as safer alternatives [5]