Anagen phase

Anagen Phase

The anagen phase is the active growth phase of hair follicles during which the root of the hair is dividing rapidly, adding to the hair shaft. This phase is one of the three stages of the hair growth cycle, the others being the catagen phase and the telogen phase.

Overview

During the anagen phase, cells in the root of the hair are dividing rapidly. A new hair is formed and pushes the club hair (a hair that has stopped growing or is no longer in the anagen phase) up the follicle and eventually out. The length of the anagen phase is genetically determined and can vary from two to seven years. The longer the hair stays in the anagen phase, the longer it will grow.

Duration

The duration of the anagen phase varies depending on the location of the hair on the body. Scalp hair typically remains in the anagen phase for several years, which is why it can grow so long. In contrast, body hair has a much shorter anagen phase, which is why it remains short.

Factors Influencing Anagen Phase

Several factors can influence the duration of the anagen phase, including:

• Genetics: The length of the anagen phase is largely determined by genetics.
• Age: As people age, the anagen phase may shorten, leading to thinner hair.
• Health: Nutritional deficiencies and certain medical conditions can affect hair growth.
• Hormones: Hormonal changes, such as those during pregnancy, can extend the anagen phase.

Clinical Significance

Understanding the anagen phase is crucial in the field of dermatology and trichology, as it helps in diagnosing and treating hair growth disorders. Conditions such as anagen effluvium, where hair falls out during the anagen phase, can be caused by factors like chemotherapy or radiation therapy.

Also see

• Catagen phase
• Telogen phase
• Hair follicle
• Hair loss
• Trichology