Types of Hair Dye and Their Mechanisms of Action

The document from 2015 detailed the history, composition, and mechanisms of action of various hair dyes, categorizing them into oxidative and non-oxidative types with subdivisions based on color durability: temporary, semipermanent, demipermanent, and permanent. It explained how temporary dyes do not penetrate the hair cortex and last until the first wash, while semipermanent dyes last up to six washes due to their higher affinity for hair keratin. Demipermanent dyes combine semipermanent molecules with oxidation dye precursors for greater durability. The document also covered the chemical composition of hair and dye penetration pathways, discussing cationic, metallic, vegetable, and permanent oxidative dyes. Permanent oxidative dyes, comprising 80% of the market, use complex chemical reactions for durable color coverage. The study emphasized understanding these mechanisms to select the best dye for different hair types, ensuring effective color application with minimal damage. Financial support from FAPESP was acknowledged, with no conflicts of interest declared.