Hair growth happens in three stages. A random number of hairs will be in each growth phase at any given time. The three stages of hair growth are the anagen stage, the catagen stage and the telogen phase. Understanding the hair growth process is sometimes helpful when discussing hair thinning and hair loss.
The anagen stage is the active phase of the hair. Cell division at the bulb of the hair shaft happens quickly, quicker than any other cell in the body. The new hair that has formed pushes out the old hair that has stopped growing. Scalp hair stays in this growth phase for two to six years. People with very long hair have a long growth cycle whereas those who are unable to grow their hair to a long length may have a shorter anagen stage. The hair on our bodies, such as on our arms and legs, has a short anagen stage.
About three percent of our hairs are in the catagen stage at any time. This transitional phase lasts for two to three weeks. Growth stops and the outer root sheath shrinks down and attaches to the root of the hair.
The resting phase for hair is the telogen phase. Six to eight percent of our hair is in this stage at a time and this phase lasts for ten days to three months. The hair follicle is at rest during this stage. It is typical to shed anywhere from 25-100 telogen hairs a day.
Sometimes the telogen phase can be affected by elements such as stress, pollution, diets and nutritional deficiencies. It can also be affected by hormonal changes, seasonal changes, aging and harsh chemical processes. Temporary hair loss can be noticed as a result of these factors.