Анотація: (English) Hair coloring is a complex biochemical process in which the acid-base balance (pH) plays a key role. The degree of cuticle opening, the rate of dye penetration, the stability of the pigment and the general condition of the hair after the procedure depend on the pH level. This article examines in detail how different pH levels affect the hair structure, the mechanism of action of different types of dyes and the quality of the final result. Research shows that highly alkaline formulations (pH 9–11) provide deep pigment penetration, but can damage the keratin structure. At the same time, slightly acidic dyes (pH 3–6) act more gently, but provide a less lasting effect. Optimum pH values vary depending on the type of dye and the desired result. Particular attention is paid to modern developments in the field of gentle coloring compositions that minimize damage without losing effectiveness. Methods of hair restoration after coloring are also considered, including the use of acid conditioners and protective agents.