Analysis of mutagenic components of oxidative hair dyes with the Ames test

Genotoxicity of oxidative hair dye precursors: A systematic review

This systematic review, conducted according to the PRISMA guidelines, focuses on genotoxicity of oxidative hair dye precursors. The search for original papers published from 2000 to 2021 was performed in Medline, Web of Science, Cochrane registry, Scientific Committee on Consumer Safety of the European Commission and German MAK Commission opinions. Nine publications on genotoxicity of p-phenylenediamine (PPD) and toluene-2,5-diamine (p-toluylenediamine; PTD) were included, reporting results of 17 assays covering main genotoxicity endpoints. PPD and PTD were positive in bacterial mutation in vitro assay, and PPD tested positive also for somatic cell mutations in the Rodent Pig-a assay in vivo. Clastogenicity of PPD and PTD was revealed by in vitro chromosomal aberration assay. The alkaline comet assay in vitro showed DNA damage after PPD exposure, which was not confirmed in vivo, where PTD exhibited positive results. PPD induced micronucleus formation in vitro, and increased micronucleus frequencies in mice erythrocytes following high dose oral exposure in vivo. Based on the results of a limited number of data from the classical genotoxicity assay battery, this systematic review indicates genotoxic potential of hair dye precursors PPD and PTD, which may present an important health concern for consumers and in particular for professional hairdressers.

Hair Dye Ingredients and Potential Health Risks from Exposure to Hair Dyeing

Given the worldwide popularity of hair dyeing, there is an urgent need to understand the toxicities and risks associated with exposure to chemicals found in hair dye formulations. Hair dyes are categorized as oxidative and nonoxidative in terms of their chemical composition and ingredients. For several decades, the expert panel's Cosmetic Ingredient Review (CIR) has assessed the safety of many of the chemicals used in hair dyes; however, a comprehensive review of hair dye ingredients and the risk of exposure to hair dyeing has not been documented. Herein, we review the safety of the various chemicals in oxidative and nonoxidative hair dyes, toxicities associated with hair dyeing, and the carcinogenic risks related to hair dyeing. While many compounds are considered safe for users at the concentrations in hair dyes, there are conflicting data about a large number of hair dye formulations. The CIR expert panel has ratified a number of coloring ingredients for hair dyes and banned a series of chemicals as carcinogenic to animals and unsafe for this application. The use of these chemicals as raw materials for producing hair dyes may result in the synthesis of other contaminants with potential toxicities and increased risk of carcinogenesis. It is an open question whether personal or occupational hair dyeing increases the risk of cancer; however, in specific subpopulations, a positive association between hair dye use and cancer occurrence has been reported. To address this question, a better understanding of the chemical and mechanistic basis of the reported toxicities of hair dye mixtures and individual hair dye ingredients is needed. It is anticipated that in-depth chemical and systems toxicology studies harnessing modern and emerging techniques can shed light on this public health concern in the future.