The anagen phase is the first stage of hair growth. It is characterized by rapid cell division in the hair follicle, which results in the production of a new hair shaft. The anagen phase is the longest stage of hair growth, and it can last anywhere from two to six years.
During the anagen phase, the hair follicle is deep in the dermis, the middle layer of the skin. The hair shaft is attached to the follicle by the hair bulb. The hair bulb is made up of rapidly dividing cells that produce the hair shaft.
The anagen phase is followed by the catagen phase, the transitional phase of hair growth. The catagen phase is a short phase that lasts for about two weeks. During the catagen phase, the hair follicle shrinks and the hair shaft separates from the follicle.
The catagen phase is followed by the telogen phase, the resting phase of hair growth. The telogen phase can last anywhere from two to four months. During the telogen phase, the hair shaft remains attached to the follicle, but it does not grow.
Eventually, the hair shaft falls out, and the hair follicle enters the anagen phase again. This process is repeated throughout a person’s life.
The anagen phase is the most important stage of hair growth because it is the only stage during which new hair is produced. If the anagen phase is disrupted, it can lead to hair loss. There are a number of things that can disrupt the anagen phase, including:
- Genetics. Some people are genetically predisposed to have a shorter anagen phase, which can lead to early hair loss.
- Hormonal changes. Changes in hormones, such as those that occur during menopause or pregnancy, can disrupt the anagen phase and lead to hair loss.
- Diet. A poor diet can lack the nutrients that are necessary for hair growth, which can disrupt the anagen phase and lead to hair loss.
- Stress. Stress can disrupt the anagen phase and lead to hair loss.
- Medications. Some medications, such as chemotherapy drugs, can disrupt the anagen phase and lead to hair loss.