- Vegetable hair dyes (henna, chamomile, and cinchona).They change color hue, are nontoxic, and last only a short time.
- Mineral or metallic hair dyes (silver nitrate or lead salts).Requiring daily use, they darken or lighten hair gradu-ally. They are potentially toxic and are incompatible with hydrogen peroxide. They may last for weeks or months.
- Synthetic hair dyes. These are classified according to wash fastness and degree of permanence as follows