Hair dyeing

Ingredients with the hair dying function give your hair a new shade or enhance an existing color. They work either as direct dyes, deposited on the surface and in the upper layers of the hair, or as substances for permanent staining, which participate in a chemical reaction inside the hair fiber. As a result, it is the hair color that changes, not the skin condition, although during application such components come into contact with the scalp, so the rules of safe use are especially important for them. The FDA notes that hair dyes can be temporary, semi-permanent, and permanent, and advises that you always follow the instructions and perform a preliminary sensitivity test. (fda.gov)

In cosmetics, this function is needed primarily in paints, tint masks, shampoos and balms to maintain color. Such ingredients affect the texture of the formula indirectly: they themselves are responsible for the shade, and the uniformity of application and durability depend on the base of the product. Typical examples are p—Phenylenediamine (PPD), one of the most well-known components of oxidizing paints, and HC Blue No. 2, a direct dye used in tint products. Mineral pigments can also be used in coloring products, for example, Iron Oxides, if the formula needs to be given a certain color nuance. The FDA specifically points out that some ingredients of hair dyes, including PPD, can cause undesirable reactions in sensitive users, so such products should not be mixed with each other and should not be overexposed on hair for longer than the recommended time. (fda.gov)