Human hair growth follows a predictable, orderly pattern. Once human hair follicles have formed, they continue to produce hair according to three recognized stages. It’s important to understand this cycle — especially since interruptions to any phase of it can lead to hair loss.
The 3 “Seasons” of the Hair Follicle
Hairs are grown by special structures called follicles. You developed your full complement of 5 million hair follicles (including the 1 million hair follicles on your head) when you were still an embryo. Let’s look at the 3 stages of this cycle.
Anagen is the active growth phase of the hair. This phase typically lasts from 2 to 6 years for scalp hair, with hair on other parts of body following a much shorter life cycle. Hair grows at a rate of approximately 1 centimeter every 28 days. As a new hair grows, it pushes out the old, dead hair that previously occupied the follicle.
Catagen is the transitional phase in which the hair detaches from its blood supply once it has finished growing. The follicle’s hair shaft starts to shrink, which helps to push the hair out of the follicle. This stage only last a few weeks for each hair.
Telogen is the dormant phase in which the dead hair remains attached to the head until it is finally shed by the follicle and pushed out by new hair. The hair is anchored by skin cells which accumulate at its base. Scalp hair remains in the telogen phase for approximately 100 days. People typically lose up to 100 hairs a day in this manner.
Any health challenge that interrupts the normal hair growth cycle can lead to alopecia (baldness). For example, pregnancy causes more hair follicles to go dormant all at once, increasing the eventual hair loss due to telogen. Chemotherapy, stress, hormonal changes and other factors can also promote hair loss. Fortunately, most of these changes are temporary in nature, meaning that your hair will grow back. Contact a Transitions Hair Loss Center by clicking here to learn more about these changes — and how we can help you cope with them!
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