The hair growth cycle has been extensively researched to gain a better understanding of how hair grows and how to treat excessive hair loss.
To better understand our hair loss, we should know more about how works grow through the hair growth life cycle, a continuous process that is divided into four stages.
What are the 4 stages of the hair growth cycle?
The four stages of hair growth are anagen, catagen, telogen, and exogen. The three first stages of the cycle describe the growth phase that creates individual hair strands and the resting phases where the hair stops growing, and the last phase describes how the hair sheds and falls out of the follicle when a new hair is growing in the root.
Anagen is the growing stage
The Anagen stage, commonly described as a growth phase or active phase of the cycle. It happens when the cells inside the root of your hair divide at their fastest rate, resulting in the growth of new hair material.
The club hair – the previous hair that was growing in the hair follicle which has now reached maturity – is pushed up by the newly created anagen hair and it eventually sheds to make room for the new hair.
Hair grows roughly 1 centimeter every 28 days throughout this active phase of hair development, and it lasts two to six years.
To summarize the key points about the anagen stage:
- It is when a hair follicle is actively growing.
- It usually lasts between 3 and 5 years, but Asian hair has a lifespan of five to seven years.
- Hair that is full length can grow until it is about 100 cm long.
Catagen is the transition phase
After the anagen phase, the hair enters the catagen phase. This is a brief transitional phase that ends the active hair growth by cutting the strand of hair off from the blood supply and the cells in the follicle that grows new hair.
The catagen phase is a transitory stage in which around 3% of all hairs are at any given time, and it usually lasts two to three weeks. The outer layer sheath is reduced and adheres to the hair root, halting growth. The creation of a club hair can be seen during this stage.
In the catagen stage:
- Hair follicles prepare to enter the dormant state.
- The deepest regions of the hair follicles begin to disintegrate.
- It usually lasts one to two weeks.
Telogen is the resting phase
The telogen phase is the third stage of your natural hair development cycle when strands reside in their follicles but are not rapidly progressing. The telogen phase lasts about three months on average, and at any time about 10% to 15% of the hairs on your scalp will be in this phase.
Even though hairs do not grow in this phase, they also do not fall off yet. In follicles that have just begun to produce new hairs during the late catagen phase, the telogen phase is about when new hairs underneath begin to grow.
In the telogen phase:
- The hair is in a stage of resting.
- For approximately three months, the follicle is dormant.
- By this time, old strands that already have reached the end of their life cycle are ready to fall out, and new hairs will begin to grow in the roots of their follicles.
Although some people believe the telogen phase to be the phase where the strand of hair is shed, many scientists have separated the telogen into two different phases. Telogen is the longer resting phase, and they have added another phase called exogen, which is the actual shedding of the hair.
Exogen is the shedding stage of the hair growth cycle
During the final stage of the hair growth cycle, individual hair strands are freed from their follicles and fall out. The follicle is now completely freed for the new hair to make roots and grow and expand.
The exogen phase is when the hair falls out and it often happens while showering or brushing your hair. You lose about 50 to 100 hairs each day, which are hairs that are in the exogen phase.
How to stimulate hairs to enter an active growth phase?
Since hair plays a big part in our general appearance, we value it and want to make sure it looks good and healthy. If the hair is thin and short, there might be a few things that can be done to stimulate its growth, boost the volume, its thickness, or overall improve its condition.
Minoxidil and hair stimulants
Minoxidil (best known under the brand name Rogaine) is an FDA-approved hair loss drug that is topically applied to stimulate hair growth. It works as a vasodilator by expanding the blood vessels and thereby increasing the blood supply, oxygen, and nutrients the hair receives, ultimately resulting in improved hair growth.
However, the drug may also cause many resting hairs to shed as newly created anagen hairs in the follicle start to actively grow and will push out the old hair. This can be an alarming experience as it will appear as hair loss instead of hair growth, but it is a part of the hair growth life cycle. For active growth, the inactive hairs will also be shed.
There are other hair growth stimulants or enhancers that are believed to work on the hair follicles in a similar way as minoxidil, such as retinoic acid and caffeine.
Microneedling for increased hair growth
Microneedling is another way of stimulating the scalp by using tiny needles to cause micro-tears in the scalp. These tiny wounds cause a healing response in the scalp by increasing blood circulation and rejuvenation. This rejuvenation process is believed to stimulate surrounding hairs to grow.
Studies have shown that men who were treated for hair loss with medication such as finasteride and minoxidil and saw little effect from their treatment, significantly increased their hair density and regrew some lost hair after adding microneedling to their treatment plan.
Frequently Asked Questions (FAQs)
Where does hair production begin?
Hair is a homogeneous keratinized epithelium composed of multi-layered flat cells with rope-like filaments which provide the hair shaft structure and support.
Hair production starts as keratin, a protein that makes up most of the hair.
The hair then grows in three unique phases: anagen, catagen, and telogen, and there may be two or more strands of hair in the follicle at the same time that goes through different phases.
Except for the bottom of the feet, inside the mouth, the lips, the backs of the ears, the palms of the hands, some of the genital areas, the navel, scar tissue, and the eyelids, human hair is produced pretty much everywhere on the human body.
How long is the hair growth cycle?
The hair growth cycle is on average approximately two to six years. During the active growth phase of this period, the hair grows about one centimeter every twenty-eight days.
In which phase of the hair growth cycle is the hair most easily lost?
Hair is easily lost during the exogen phase, as that is when the hair is liberated from the follicle and falls out of the scalp. It often happens when it is helped by shampooing, showering, scratching one’s scalp, or combing one’s hair.
It’s normal to lose fifty to a hundred hairs per day, and they are mostly hairs that are already in the exogen phase. When hairs are in this phase and they don’t fall out today or tomorrow, they will eventually fall out during the next two to five months, and new hairs will grow in the follicles while the old hair sheds.
If cells are replaced every 7 years, does hair change every 7 years?
Hair is not made up of live cells, but of dead cells and a protein called keratin. Every seven to ten years, it is said that the body’s cells replace themselves. The cell renewal process is faster in some sections of the body, but it can take a decade or more to rejuvenate the entire body.
If you let your hair grow and never cut it, it will eventually change and replace itself as all the hairs on the entire head have gone through the entire hair growth cycle. This can take up to eight years, and the hair can have grown more than a meter (or more than 3 feet and 3 inches) by that time.
What are the signs of new hair growth?
Typical signs of new hair growth are dark spots on the scalp, fine and short hair appearing, reduced hair loss, thicker hair shafts, and stronger strands.
Hair loss can be painful and take a long time to recover from. Waiting for them to grow back feels like an eternity. When hair thinning occurs regularly, it can take many months for the hair to regrow.
Conclusion & Summary
To quickly summarize, these are the four stages of hair loss:
- Anagen: It is a term used to describe the process of the growing phase of your hair. Our hair length is determined by the growing phase, which lasts 2-7 years.
- Catagen: It is a term used to describe the transition phase of your hair. Catagen is a ten days transitional stage. The dermal papilla decreases as the hair follicle diminishes and pulls away.
- Telogen: It is the resting phase and it is a three-month-long resting phase. This phase affects around ten to fifteen percent of the overall hairs. A hair growth commences its growing phase while the old hair is resting.
- Exogen: It is described as a new hair phase. This is a portion of the resting period, during which the old hair loses and new hair grows. Hair shedding is generally typical when fifty to one fifty hairs fall out per day.