Hair grows at a rate of 1 to 1½ cm per month. Its growth, which is variable from one individual to another, takes place during the pilary cycle. Each cycle has 3 successive phases:
• the growth or anagen phase: this phase, which is the longest in the cycle, lasts for 3 to 5 years. Little by little the hair shaft becomes longer. The hair is growing;
• the transitional phase or the catagen phase: the hair stops growing for 2 to 3 weeks; it is the resting phase.
• the elimination phase or telogen phase: the hair falls out and frees the pilary follicule so that ‘new growth’ can start. This phase, which lasts for 2 to 5 months, is characterized by the total absence of cellular activity.
Hair grows, lives and dies. Dead hair falls out and is replaced by new hair.