They use a “booster” effect: they have a higher load of pigments and higher levels of ammonia.
They have difficulty in lightening natural hair.
The colour is progressive after 10 minutes of processing the oxidation continues giving a darker level in respect to the chosen shade.
The high concentration of pigments can increase scalp sensitivity and create break lines with prolonged use.
The high percentage of ammonia causes damage to the hair and affects the duration of the color.
It is necessary to mix the fashion shades with the natural tones to obtain grey coverage.
With continued use the high concentration of pigments makes hair dull and brittle, and progressively darker with each application.
Rarely is is the result true to color swatch, but instead darker and more matte.