The average human head has around 90,000 –120,000 hair follicles, growing at an average of 0.5 to 1 centimetre per month. Each hair follicle follows a cycle of growth until it sheds at the end of the cycle. There are 3 main phases in the hair growth cycle:
1. ANAGEN (GROWING) PHASE
- Growth phase of the hair follicle and new hair is formed.
- Approximately 85-90% of the hair follicles spend 2 – 5 years in this phase.
- This is the only phase where laser therapy is effective.
2. CATAGEN (TRANSITION) PHASE
- Intermediate phase of hair growth.
- Lasts for 1 – 2 weeks.
- The dermal papillae - a group of cells that contain blood vessels and nutrients supplying the hair follicle, begins to separate from the hair follicle.
- Hair follicles slowly transition into the resting phase.
3. TELOGEN (RESTING) PHASE
- The dermal papilla is completely separated from the hair follicle.
- Old hairs reach the end of their cycle and falls out.
- Lasts for 3-4 months.
- At the end of this phase, new hair growth is initiated.