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How Hair Growth Works?

How Hair Growth Works?

Jul 21, 2022

Ako Stark

How Hair Growth Works

Hair growth and loss often seems like a simple process, but that just isn’t the case. Hair growth is a cycle of 4 phases that cover the actions of growth, to shedding. This cycle has seen an immense level of study, helping us understand just how hair growth works and how we can stop its loss. 

The Four Phases of Hair Growth

Hair growth and hair regeneration are both part of a cyclic process, covering four distinct stages: Anagen, Catagen, Telogen and Exogen. The process begins with a new hair in the follicle, the growing of the hair until it stops is released from the follicle. 

Hair grows from the follicle, or the root which is underneath the skin. At the base of the follicle is a blood vessel that feeds the hair 


Anagen is the stage of hair growth that takes the longest out of all the others. In this phase, quite simply: growth. It is a period of active hair fiber production. While it is potentially the longest running phase of hair growth, the length of time for different people, and other mammals can vary heavily.  There are six sub stages that make up the Anagen phase, Anagen I-VI; lasting only a few weeks in mice, but up to 5 years in humans.  An influx of cells at the beginning of the anagen phase is paired also with an increase in ECM material. The size of the dermal papilla is thus double. A thing called axial symmetry in the hair bulb will determine the curvature of the hair’s final structure. 

The dermal papilla sends signals to the surrounding matrix cells, the positions of which are then set in stone. An example of this would be the central cells becoming the medulla. The differentiating matrix cells caused the formation of precursor cells that stem from different follicle lineages. Then a series of specialized differentiations goes on in which defined sets of keratins form seven concentric epithelial lineages of the follicle, beginning at the medulla and ending at the companion layer. While this happens, the outer root sheath, the outermost layer of the follicle is grown from the bulb. 

85%-90% of all the hair on a human head is in the Anagen phase. 


When the Anagen phase ends, the Catagen phase begins. This is a process of about 10 days, in which the hair follicles shrink, causing actual hair growth to stunt. In this phase the bulb of the hair, which is inside the follicle, disconnects from the follicle. The hair may still grow, if only slightly during this phase, separating from the bottom of the follicle which will eventually stop the growth of the hair. The bulb then begins a process where it breaks down, shrinking and causing the shrinkage of the follicle. 

5% of all hair on a human head is in the Catagen phase.  


The Telogen lasts a bit longer than the Catagen phase, about 3 months,  and is often referred to as the resting phase in hair. Hair growth stops completely during this phase. The phase is characterized by the growth of new hair bulbs in the follicle. 

Some experts view the Telogen as the final stage for a hair, because at this point, the growth of a new hair has already begun. The hairs in this phase, however, do not fall out. 


The Exogen phase is often referred to as the shedding phase. This phase is also viewed by some experts to be an extension of the Telogen phase. During the Exogen phase, hair is released from the scalp, though often does not reach full removal until after washing or brushing.  50-100 hairs go through this process per day and is completely normal in the hair growth process. The Exogen phase can last for up to 5 months, while the hair bulbs born in the previous phase have already begun the Anagen phase. 

Also Read: Are Hair Growth Products Safe?

Maintaining Hair Health

Given the four main phases of hair growth, the growth of hair is still varied between individuals due to hormonal and genetic circumstances, or in other words, things largely out of our control. There are still some things we can do to maximize the health of our hair in our everyday lives. 


Nutrition is important for all aspects of health, but the impact of nutrition on the health of hair is often overlooked due to the overwhelming amount of marketing placed in hair solutions. Hair is largely protein based, so a diet that includes healthy proteins is necessary for hair growth, especially in the Anagen phase. 

Including these things in your diet will help:

  • ✓ lean meats
  • ✓ fish
  • ✓ beans
  • ✓ legumes
  • ✓ low-fat dairy products

Vitamins are important for any diet no matter what, but here are a few that are proven to have great results with hair maintenance. 

  • ✓ Vitamin D
  • ✓ Vitamin C
  • ✓ Iron 
  • ✓ Zinc,
  • ✓ Folic Acid
  • ✓ Vitamin B12


Many people ignore the effects of a stressful life on hair maintenance. Stress is one of the leading causes of hair loss, but they typically delve into two of three most common conditions that promote hair loss.

Telogen effluvium is a condition that accelerates the growth of hair in the Anagen phase. Whereas the hair would likely grow longer for a longer period of time, a hair that is not yet ready would be separated from its follicle prematurely. And since the Anagen phase is the only phase affected, more hair is removed from the scale than is growing on the scalp.. This condition can double or even triple the rate of hair loss in an individual. 

Trichotillomania is a psychological condition that does not affect the growth process of hair, but the behavior of someone. Those with this condition are met with the irresistible urge to pull hair from the scalp typically, as well as other parts of the body. While much of the initial hair loss is in fact due to the pulling of the hair, the follicles will be damaged stunting hair growth over time. 

Alopecia areata is a condition in which the immune system attacks healthy hair follicles. These follicles are then not allowed to grow, effectively being killed by the same blood that is passing through them while they are connected. Traction Alopecia is a form of alopecia caused by the pulling of hair follicles commonly in tight hairstyles over long periods of time.

While the most optimal situation for hair growth involves a lifestyle with no stress, that is simply unrealistic.  The resulting hair loss  from a stressful lifestyle may not look like much at first, however as the rate between hair growth and loss widens the effects will become more apparent.  It is important to recognize the level of stress somewhat preemptively. Stress does not only affect hair growth, but hair color as well. 

At the start of proper hair care is choosing the right solutions for your hair type. Take into consideration the different aspects of your hair. Be sure to consider things like:

  • ✓ Volume
  • ✓ Curls
  • ✓ Coarseness
  • ✓ Softness
  • ✓ Oil 
  • ✓ Dryness
  • ✓ Brittleness 

Be sure to also consider the conditions of your hair at both the root and the ends, as maintenance on both ends of the hair is crucial to a healthy head of hair in the long run. Be wary of things like split ends which if not properly handled can result in damaged stunted hair growth. Watch out also for hair thinness at the base which may indicate things like Telogen effluvium. 

Shampoo and Conditioner 

The kind of shampoo you use as well as how you use it is also important. Therefore, understanding the role of shampoo is just as important as using it. Shampoo is designed primarily to strip the hair of certain oils in the hair, those that are not generated by the scalp itself. Shampoo may also be good for stripping away older oils on the scalp which will promote the circulation of oils on the scalps. 

Hair ends are already much dryer in comparison to roots because oils are not created from the hair, but from the scalp. That being said, do not apply shampoo to the ends directly, but to the roots, allowing the runoff of shampoo to indirectly work on the ends when rinsing.

Conditioner is designed to do the exact opposite of shampoo. Where shampoo is designed to strip oils away from the head, conditioner is designed to add them back. However, the scalp already produces its own oil for the hair roots. Therefore, it is not necessary and can even hurt hair health to constantly apply conditioner to the root. This can lead to very oily hair and a disproportionate amount of oil on the scap compared to that on the hair ends. Apply conditioner only to the mid part of the hair to the ends for the best results. 


There are four phases that govern the growth of hair. These phases are a part of a cycle hair goes through that controls the amount of hair on and not on the head at a particular time. While the growth rate of hair in individuals varies due to uncontrollable genetic and hormonal circumstances, there are strategies to help maintain or increase the natural rate of hair growth. On the same coin though, there are just as many ways hair loss can occur, whether through improper hair care, stress, malnutrition, mental or medical conditions. 

If you are suffering from hair loss, or are concerned that your hair may not be growing at its proper rate, be sure to visit a doctor and consider trying Universal Hair Growth Oil. Our natural formula is designed to strengthen already growing hair and promote healthy hair growth for years to come.