The average person is born with 100,000-150,000 hair follicles on their head. Where are those hair follicles now?
On the floor, your pillow, the shower drain, and your brush. But, is this normal? Typically, the average person sheds 50-100 hairs a day as part of the hair growth cycle. Understanding the phases of the growth cycle and how they relate to hair loss, helps to start with the biology and anatomy of hair.
The Biology and Anatomy of Hair
Hair strands are primarily made up of a protein called keratin and grow from hair follicles in the skin. At the base of each hair follicle is a living bulb. Inside the bulb, active cells divide and grow to create hair. Blood vessels provide nourishment for the bulb and deliver hormones that impact hair growth.
Disruption to the Hair Growth Cycle
Hair loss occurs when there is a disruption to the natural growth cycle. A variety of factors can interrupt the cycle, including genetics, age, poor nutrition, extreme stress, illness, prescription medications, hormonal changes, and diseases. When the cycle is disrupted, or if a hair follicle is damaged, hair may fall out faster than it can be regenerated, which can lead to overall thinning, patchy hair loss, or a receding hairline.
The Four Stages of the Hair Growth Cycle
Hair grows at an average rate of a quarter to half an inch per month. As your hair grows, individual strands randomly cycle through four, ongoing phases: growing, transitioning, resting, and shedding. Understanding the natural growth cycle of your hair helps explain how disruptions in the cycle can lead to hair loss.
- Anagen (Growth Phase): This is the active phase of hair growth. As many as 85 to 90 percent [SA2] of the hairs on your head are growing at any given time. Each strand is in the growing phase for 2-7 years.
- Catagen (Transitional Phase): Over a few weeks, hair growth slows as follicles shrink. About 3% of all hairs are in the transitional phase at any one time.
- Telogen (Resting Phase): In this phase, the hair follicle is entirely at rest and no longer growing. Around 6 to 8 percent [SA3] of all hair is in the resting phase at any given time. The resting phase typically lasts a few months.
- Early Anagen (Shedding Phase): At the end of the resting phase, the hair will gradually detach from the follicle and fall out. Therefore, the average person sheds between 50-100 hairs each day.
It’s important to note that the last three phases (transitional, resting, and shedding) combined take place for approximately 3-4 months. That’s why it takes at least 3 to 4 months before you start to see results from any topical, laser, supplemental, or surgical treatments for hair loss.
