Hair growth occurs in three different phases alternating active cycles and resting cycles:

  • anagen phase (growing);
  • catagen phase (regressive);
  • telogen phase (resting).

Anagen phase
It is the phase of hair active growth and typically lasts from 3 to 6 years. The cells of the bulb multiply and permit hair growth. During the anagen phase hair grows about 0.3-0.4mm per day.

Catagen phase
It is the hair regression phase and typically lasts from 2 to 3 weeks. Cells stop multiplying and the hair follicle undergoes several morphological and metabolic modifications. Its lower segment disappears, the bulb becomes smaller and goes up towards the surface, the stem stops growing.

Telogen phase
It is the hair resting phase, during which the follicle is completely inactive. Hair is inside the follicle, held up by scarce intercellular connections that keep it in the scalp until the beginning of a new anagen phase and sometimes even for more subsequent phases. The telogen phase typically lasts from 2 to 4 months and ends up with hair loss.