Basic Blue 99

FunctionSemi-permanent basic dye

What it is — Basic Blue 99 (INCI: Basic Blue 99) is a cationic, or *basic*, hair dye. Unlike the oxidative dyes used in permanent colour, it carries a positive charge and is used ready-made rather than developed with peroxide.

What it does — Hair damaged by washing, sun and heat carries a slight negative charge, so a positively charged dye is drawn to it and settles on the outside of the strand. That is why basic dyes deposit tone rather than change the hair's own pigment: the colour sits on the cuticle instead of forming inside the cortex. It builds gradually over repeated washes and fades gradually once you stop.

Typical use — Toning and gradual grey-covering shampoos, conditioners and semi-permanent colours, usually as part of a blend with other basic dyes to mix a shade. Blue 99 supplies the blue-black end of that blend.

Who it suits / good to know — Because there is no peroxide and no oxidative-dye chemistry, it avoids the PPD-class sensitizers that drive most hair-dye allergy. The trade-off is coverage: tone builds over many washes and never reaches the density of a permanent dye. It can also temporarily stain skin, nails and light towels, and lighter or more porous hair takes the tone more strongly.

Safety — DHALIORA grades it mid risk. Basic dyes are far less sensitizing than oxidative dyes, but they are still colourants that sit on skin and scalp during use, and reports of contact sensitisation exist. This reflects the ingredient in general and is not medical advice; patch-test if your scalp is easily irritated.