Phases of hair growth.

What Are the Phases of Hair Growth?

Every day, the average person loses between 50 and 100 hairs.

That loss is part of the normal hair growth cycle. But when you have alopecia areata (AA), your hair doesn’t follow that same pattern. 

If you have alopecia areata (AA), understanding how hair grows is an important part of understanding your hair loss, treatment, and what regrowth might look like. To help you in this understanding, we’re breaking down the four phases of hair growth.

Let’s have a look at how that works. 

The Four Phases of Hair Growth & Alopecia Areata

Your hair follicles grow and shed hair in a cycle. Each component of that cycle is called a phase, of which there are four.

The cycle begins with the long growing phase, then enters a transitional phase, moves to a resting phase, and finally culminates in a shedding stage, which is when the hair falls out. Then, a new hair begins to grow in the follicle and this starts the cycle all over again. 

The length of these phases varies depending on the individual as well as the region of the body. For the average individual, as many as 100 hairs reach the shedding stage every day and fall out. But when the cycle is disrupted, or the follicle is damaged, it impacts the functioning of these phases and more hair may fall out or hair may fall out more quickly than it can be generated. AA is an example of disordered hair follicle cycling. 

The Anagen Phase

The anagen phase is the long growing phase. It’s called the long growing phase because it can last anywhere from three to five years.

This is when your hair follicle is actively pushing out the hair. That hair continues to grow until it reaches the shedding stage.

Experts believe that it’s this phase that’s interrupted in individuals with AA. It’s believed that the immune system attacks the hair bulb, causes inflammation, and this inflammation leads to anagen arrest. Anagen arrest is a disruption of the growing phase which leads to abnormal loss of anagen hairs.

The Catagen Phase

The catagen phase is a short transitional phase that begins when the anagen phase ends. This phase only lasts approximately 10 days.

During the catagen phase, the hair follicle shrinks which leads to slower hair growth. Nearing the end of this phase, the hair itself will separate from the hair follicle, though it continues to grow and remains in place. 

The Telogen Phase 

The telogen phase is the resting/retaining phase. It usually last about three months.

In his phase, the hair has stopped growing from the follicle. While the hair isn’t quite ready to shed yet, a new hair will begin to form in the follicle.

The Exogen Phase

The final phase of hair growth is the exogen phase, which is the phase in which the hair is shed. This lasts between two and five months.

The exogen phase is sometimes considered an extension of the telogen phase. But it’s this phase wherein the hair is released from the scalp. Washing or brushing your hair usually helps this process.

More Helpful Hair Information

There are four phases of hair growth: the anagen, catagen, telogen, and exogen phases. These phases start with the hair follicle pushing out the hair and end with the shedding of the hair. But in individuals with AA, this cycle is thought to be interrupted in the very first phase.

Understanding this process gives you a little more insight into where hair loss occurs and why. And for more helpful hair information like this, be sure to check out our blog regularly.

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