Written By: Zenani Sizane
Each of us has distinct hair that behaves differently for every single person. Because of this, it's critical that we are aware of and comprehend the traits and behaviors of our own hair in order to properly care for it and ensure its success.
With that being said, it is also important to know how our hair is structured on a broader spectrum. Though everyone has unique individual hair, the hair is also structured to work in a certain manner, there is a process in which hair grows and sheds, and this process is known as the hair growth cycle; and this cycle consists of four key stages that the hair goes through a process of growing, resting, transitioning and shedding. In this article, we deem it useful to understand the hair growth cycle in order to recognize and understand many of the problems you can encounter with your hair.
The Hair Growth Cycle Phases
The hair growth cycle consists of 4 stages in the growth phase; the anagen phase is considered the first phase of the hair growth cycle, this is the growth phase, which can last between two and six years. This phase and its length determine how long the hair becomes. The catagen phase, also known as the regression phase, comes next and only lasts about one to two weeks, during this time, the hair follicle shrinks and detaches from the dermal papilla. The third phase is the telogen phase, which lasts about five to six weeks. The fourth and final phase is exogen, this is when the hair eventually detaches and falls out.
In the following sections of the article, we are going to unpack each phase individually and look at how we can identify when our hair is in each phase and furthermore how we can ensure that our hair is well taken of in each phase and look at the steps we can take along the way to help ensure that your hair follows a healthy growth cycle. This is going to be a useful tool to use in understanding proper hair care especially in terms of regressing hair or hair loss.
Stage 1- Anagen Phase
Growth Phase
Your hair grows around half an inch a month and faster in the summer than in the winter. During this phase, your hair follicles begin producing new cells, called keratinocytes in preparation for new hair’s emergence. A new hair pushes old hair that stopped growing up and out of the follicle.
As long as the hormones that regulate it are present, this process will continue, which is why men typically notice that their hair grows faster than women's does as each year goes by. In addition, the anagen phase of hair on your legs, arms, and lashes lasts for only 30 to 40 days, making it shorter than the hair on your head.
An average full length hair measures between 18 and 30 inches, as the growth phase, also known as the anagen phase, lasts for three to five years. How long you can grow your hair depends primarily on how long the anagen phase lasts for each individual. People of Asian origin typically have longer anagen phases in their hair, which can last up to seven years and allow hair to grow up to one meter.
The anagen phase is an active phase where hair matrix cells divide and push the hair shaft up and out. Up to 90% of our scalp hair is in anagen phase at any given time. The amount of time that a hair follicle stays in the anagen phase is genetically determined.
Some people naturally have longer anagen phases and can grow their hair very long, while others will never see their hair get much longer than 1.5 feet.
An unknown signal causes the end of the anagen phase. A number of things, including environmental or genetic factors, can disturb anagen hair growth, resulting in hair loss or the inability to grow long hair.
What affects the anagen phase:
A decrease in the number of hair follicles growing can cause more hair follicles to go into the telogen phase at the same time. This results in less time spent in the anagen phase overall and a type of diffuse hair loss known as telogen effluvium. Those with the condition may have hair that is noticeably thin.
Common causes of telogen effluvium include:
High fever caused by an illness
Childbirth
Surgery
Severe emotional stress
Poor nutrition
Significant weight loss
Certain medications
Stopping hormonal birth control
Anagen effluvium is a form of hair loss that occurs due to injury of the hair follicle during the anagen phase, chemotherapy is a common cause:
Causes
Radiation
Toxic heavy metals
Toxic chemicals
Inflammatory disease
These disrupt the hair while it is in the growth phase, leading to diffuse and often abrupt hair loss. In such cases, the hair will usually recover to its prior fullness once the offending agent is stopped.
Related Conditions
Short anagen syndrome and loose anagen syndrome are two conditions that can affect this phase of hair growth, irrespective of the cause listed above.
Short Anagen Syndrome
Short anagen syndrome is a rare condition that shortens the anagen phase. People with this syndrome say that their hair does not grow and/or they have never needed a haircut. An exam will reveal a predominance of telogen hairs. The cause of this syndrome is unknown.
Loose Anagen Syndrome
Loose anagen syndrome is seen in some children, hair is sparse and can easily and painlessly be pulled out. If it is, the roots show that hair is in the anagen phase. This condition is caused by a defect in the way the hair is attached to the scalp. It may be an inherited condition, and it usually improves as the child ages.
Can anagen stimulators increase hair growth
Some hair products claim to be ‘anagen stimulators’ that either induce hairs to go into the anagen phase or help hairs stay in the anagen phase longer.
Rogaine(minoxidil) is a topical medication that stimulates hair growth:
Causing telogen hair follicles to enter into the anagen phase and lengthening the anagen phase.
Although this medication is approved by the FDA, we suggest doing your own research and first talking to the specialized healthcare professional- ideally a professional who specializes in treating hair, skin and nails.
What can you do to maintain healthy hair during the anagen phase
This is the growth phase of the hair cycle. To maintain healthy hair during this stage, it is important to eat a balanced diet and get enough sleep. Additionally, it is important to avoid stress and environmental pollutants.
After the anagen phase
After this, your hair goes through three more phases–catagen, telogen and exogen phase. It is important to note that all hairs do not go through these stages at the same time. The reason you temporarily go bald is that, at any given moment, some hairs are in the anagen phase, others are in the catagen phase, and the remaining are in the telogen and exogen phase.
Stage 2- Catagen Phase
Transition Phase
The catagen phase is a short transition stage that occurs at the end of the anagen phase. It signals the end of the active growth of a hair. It lasts approximately 16 days, which is 2-3 weeks. Keratinization of the hair occurs here as keratinocytes produce their last bit of keratin and die off, 2% of all scalp hair are in this phase at any given time.
The hair detaches from its blood supply during the catagen phase. The outer root sheath then shrinks and attaches to the root of the hair, forming a club hair, which is a fully formed hair that has stopped growing.
During this time, your hair follicles become dormant but don't necessarily start shedding anything immediately. Because this stage occurs so close to anagen phase, there will probably still be some visible hair while moving into the catagen.
In order to maintain hair health during this transition phase of the hair cycle, it is important to avoid tight hairstyles and harsh chemicals.
Stage 3- Telogen Phase
Resting Phase
After the short catagen phase, approximately three weeks after the onset of catagen or seven months after your body began producing new cells in anagen, the hair is released and the hair follicle rest for three months. Old hairs are replaced with new ones and your body releases them from their resting stage via eccrine glands located around the base of each hair follicle called vellus follicles.
About 15%–16% of the skin cells on the scalp are made up of these vellus follicles, which shed often without posing any serious problems. If not, all of your hair would fall out at once. Instead, each follicle is independent and goes through the hair cycle at different periods. Rather, on a healthy head of hair, you shed just a specific number of hairs each day—up to 80 hairs; nevertheless, if you suddenly start noticing excessive shedding during life or after menopause, you may have alopecia areata.
Hair loss, hair thinning and problems with hair growth occur when the growth cycle is disrupted. This can be triggered by conditions such as nutritional deficiencies, medical issues, stress or illness. If your hair growth cycle is consistently challenged, you may find your hair will not grow as long as it previously used to.
This is due to your hairs are never allowed to stay in the anagen phase by enough for your hairs to reach the desired length and that is because the anagen phase is cut short and the hair may enter the telogen phase and a great amount of hair will shed, and this excessive shedding is known as telogen effluvium.
What is Telogen Effluvium
Telogen effluvium is the second most common cause of hair loss, trailing only after androgenetic alopecia. To better understand telogen effluvium, consider a few facts about hair: at any time, the individual hairs on your scalp are in different phases; some are growing, and the others are resting.
Normally, 90% of hair is in the anagen phase, which is the phase of growth. For numerous years, a single hair can grow half an inch every month while it is in the growth phase. The remaining 10% of hair is in the telogen phase, sometimes referred to as the resting phase, which permits the hair follicle to develop, nourishes individual hairs, and then relaxes in preparation for the production of new hairs and the renewal of the growth cycle.
It is normal to lose about 160 hairs each day, however in the telogen effluvium, more hairs than normal enter the resting phase and are shed. The trigger for hair loss commonly occurs 3 months before hair loss is noticed before it usually takes that long for a long to go from anagen to telogen, however in some cases no triggers are identified.
Acute Causes of Telogen Effluvium
Childbirth
High Fever
Surgery
Severe illness
Sudden or extreme weight loss
Severe Emotional stress
Unbalanced diet
Chronic Causes of Telogen Effluvium
Rather than a greater percentage of hair suddenly entering the telogen phase; the hairs go into the rest phase as they normally do, but they stay in it longer. The longer rest delays the hair’s return to a growth phase.
Another type of telogen effluvium can occur when the trigger that disrupts the hair cycle is ongoing, for example, a thyroid disorder or nutritional deficiency. Since the trigger is ongoing the onset of hair loss is more gradual, and it lasts longer with this type of telogen effluvium.
Symptoms
Diffuse thinning of hair- this means that the hair loss occurs across the entire scalp rather than a few bald spots
In more severe cases, hair loss may be noticed in other areas of the body such as under the arms, and the pubic areas
There are no other associated symptoms like itch, pain or redness of the skin
Diagnosis
Your dermatologist or primary medical doctor can diagnose the condition based on your detailed medical history, description of your symptoms and examination of your scalp and hair. They may gently tug on your hair and look to see how many hairs are falling out and what phase of the hair cycle they are in.
In some cases, blood tests may be needed to measure your levels of thyroid hormone, iron, vitamin B12, and folic acid to rule out abnormalities of these as a cause for hair loss. A skin biopsy of your scalp might also be helpful.
Treatment Options
No treatment is needed for telogen effluvium since it's a condition that gets better on its own. There is no permanent damage to the hair follicles, and new hairs grow in the place of those lost.
This is especially true in cases due to short-lived causes such as childbirth or an illness that you have recovered from. In cases where telogen effluvium is caused by ongoing stress to the body such as an overly restrictive diet or chronic emotional stress, hair loss will not stop until the underlying cause is resolved.
Therefore, in order to maintain healthy hair during the telogen phase, it is important to avoid trauma to the scalp and excessive brushing.
Stage 4- Exogen Phase
Shedding Phase
The exogen phase is the final phase of the hair growth cycle, however it’s more of an extension of the telogen phase. This is the phase where hair strands are released from the hair follicles also known as hair shedding. This can last for as long as 2 to 5 months during which new hairs are growing in the follicles and in essence replace the old ones. You may notice between 50 to 100 hairs fall out during this time, however, don’t panic as this is totally normal daily hair loss.
A decline in anagen or even hair thinning or loss can result from disturbances in the hair cycle. Illness, poor diet, or abnormalities in metabolism can all lead to disturbances. Stress can also lengthen the hair cycle's resting period, which prevents as much hair from growing back into the anagen phase. After this phase ends, the cycle restarts in the anagen phase.
This is the shedding phase of the hair cycle. To maintain health during this stage, it is important to eat a balanced diet and take supplements. Additionally, it is important to avoid stress and environmental pollutants.
How to maintain healthy hair during all four stages
Having healthy, fuller hair depends on genetics and hormone levels, which are largely beyond your control, as well as manageable factors related to a healthy lifestyle and proper hair care.
Good Nutrition
Hair is largely made of protein; therefore, you should keep up your protein intake by focusing on healthy proteins, which includes:
Lean meats
Eggs
Fish
Beans
Legumes
Low-fat dairy products
There are also some good nutritional supplements to help maintain hair health, according to the 2019 study in the journal Dermatology and Therapy, these include supplements that contain biotin, iron, vitamin C, vitamin D, vitamin B12 folic acid, zinc and omega-3 fatty acids.
Minimizing Stress
If you are experiencing stress, your hair may spend more time in the resting phase of the growth cycle. This means that new hair won't be growing as quickly. To help your hair it is important to find ways to manage and reduce stress. You can always try different techniques and exercises such as meditating, breathing exercises and counseling to help you in your quest to reduce stress.
Proper Hair Care
To have healthy hair, you need to be mindful of the products you use and how you treat your hair. Start by finding shampoos and conditioners that are designed for your hair type, whether oily, dry, fine or color treated. You may need to try a few different products before you find ones that work well for you. Pay attention to how your hair responds to different shampoos and conditioners.
Be gentle with your hair to avoid damaging it. Avoid very hot water when you shampoo and dry your hair with a microfiber towel or an old cotton t-shirt, hair is more vulnerable to damage when it is wet. Turning down the heat when drying your hair or letting your hair air dry whenever possible to minimize heat damage will make all the difference.
Final Thoughts
The purpose of the hair development cycles is to help you recognize that your hair has a life of its own. By knowing the stages your hair goes through, you can take proper care of it and encourage its growth—something we all want.
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