Hair Growth Science Explained and How Transplants Can Help

Hair, its texture, and how quickly or slowly it grows all differ from one person to the next. Additionally, hair means so many things to different people that the thought of losing it can be, well, hair-raising.

But what we see on our scalps is just half the story. The rest is under the scalp, where several processes, genetics, lifestyle choices, and other variables determine hair growth. To further muddy the waters, theories about growing hair faster are all over the internet—some truthful, and some not. 

One way to understand your hair better and separate fact from fiction is by understanding the science behind hair growth. And we are here to help you do just that. 

Let’s begin at the root of the matter!

Hair Follicles Explained

Hair follicles are tube-like structures in the skin that grow hair. Every individual is born with millions of hair follicles spread out in parts of the body where hair grows. These sprout hair as you age. 

Each follicle looks like a tube or cylinder with a rounded bottom, and it sits around the root of a hair strand. At the top of the cylinder is an opening where hair shoots out from. Hair follicles are among the few structures of the body that can cease functioning and start functioning again (degenerate and regenerate). 

Their ability to do this helps with hair growth on your head and body. However, hair follicles can also get damaged, leading to slowed hair growth or loss. 

The Function of Hair Follicles

While one of their primary functions is to grow hair, hair follicles have additional functions. These include:

  • They assist the skin in repairing itself after an injury or a wound
  • They form new blood vessels (angiogenesis)
  • They create new nervous system neuron cells (neurogenesis)

Hair Follicle Location

Hair follicles originate from the first and second layers of the skin, and are on all parts of the body that grow hair and. The two layers of skin are known as the epidermis and the dermis.

Sometimes, follicles holding hair on your head, eyebrows, and lashes can go into the third layer of your skin structure, known as the subcutaneous tissue or hypodermis. 

If you pull on a hair strand, you might notice a ball or bulb on one end. This is not a follicle but a hair root that grows from the follicle. The root grows back, and so does your hair. 

If you accidentally damage your hair follicles, these grow back as well, and hair growth can continue. However, it can take up to four years to regain hair growth after follicle damage, depending on the degree of damage. 

Still, be mindful of your follicles, as frequent injuries can cause scarring, which can hinder or stop hair growth. Scarring can also yield thinner, less sturdy hair. This makes you more susceptible to hair loss at the injured sites. 

What Is The Hair Growth Cycle?

The hair sprouting from your follicles goes through several stages known as the hair growth cycle. Here is a detailed look at each phase of hair growth.

Anagen (Growing Phase)

The anagen phase is also known as the growth or the active phase. Understandably, you would want your hair to be in this phase permanently and in overdrive. 

Unfortunately, the initial growth phase lasts three to five years, during which your hair grows about 1 inch every 28 days. Here, the cells in the roots of your hair are rapidly multiplying, forming new hair. 

Interestingly, this stage lasts longer for people of Asian descent and is faster in summer than winter!

Catagen (Transition Phase)

After a period of growth in the anagen phase, your hair enters a short, transitional phase known as catagen. This phase ends active hair growth and separates individual hairs from receiving blood supply from hair-producing cells. When the blood supply is cut off, hair strands are deprived of nutrients and stop growing. At any one time, 3% of your hair is in this stage. 

This chapter lasts ten days. At this point, hair also begins detaching from the bottom of the hair follicle but remains in place. 

Telogen (Resting Phase)

This is the resting phase, where existing hair on the scalp starts going into a dormant phase while new hairs grow underneath. This goes on for about three months. The resting part is noted in that hair does not grow nor fall off in this stage.

Exogen (Shedding Phase)

Some experts consider the exogen phase part of the telogen phase, while others categorize it all on its own. 

The shedding phase is when hairs detach from the follicles entirely and fall out of the scalp. This process is helped along by any traction on the scalp and hair, including brushing and washing. 

This phase sticks around for 3 to 5 months, and you typically lose 50 to 100 hairs daily. As this happens on the surface, new hairs are growing in follicles underneath.

Factors that Affect Hair Growth

Some people grow long, bouncy, thick, lustrous hair with no effort at all. Others over-pamper their hair with products and special hair treatments and don’t make any headway. 

What gives?

Here are some variables that affect hair growth. 

Hormonal factors

Hormones, in both males and females, make a significant contribution to hair growth. The culprit here is a hormone known as androgen. 

Androgen is responsible for hair growth in men and a little bit in women as well. However, as we age, androgen levels begin to drop. With this drop comes slower hair growth rates, less luster, and thinning. 

For women of a certain age, lower estrogen and progesterone levels have the same effect.


Genetics are responsible for many of our features, including hair texture, density, and growth rate. Female and male pattern baldness results from hereditary hair loss. 

Males susceptible to baldness convert testosterone into Dihydrotestosterone (DHT). DHT attaches itself to cells in hair follicles and damages them, slowing down or stopping growth, which causes baldness. 


Research tells us that stress forces the hair to enter into the resting and shedding phase of the hair cycle prematurely. As such, severe psychological stress can cause telogen effluvium, characterized by hair loss and thinning. 

So work on your sleep hygiene, work out to get endorphins pumping, and engage in other stress busters.


A healthy diet is great for your whole body’s health, including your tresses. The best way to get the nutrients you need is from your diet. If you cannot do so for varying reasons, you can consider supplementing. 

Protein, for one, is among the building blocks of hair. As such, protein-rich foods can help promote healthy, strong hair. Similarly, a biotin deficiency is known to cause alopecia, which is a partial or complete hair loss. Additionally, selenium, iron, zinc, vitamin E, D, and A deficiencies are known to aggravate hair loss. 

Harmful hair care practices

That ultra slicked-out hair might look great, but it doesn’t do much for hair health. Some hair styling practices, for example, blow drying, flat ironing, and hair straightening can overheat the hair, making it brittle. Dry, brittle hair is more susceptible to breakage and falling off. 

Another harmful hair practice is tight hairstyles. These might look neat but create too much tension, especially on the hairline. It’s common to see severe hairline loss and recession in women who get their weaves and braids done too tightly. 

Hair products containing harsh chemicals can also strip hair of its natural, protective oils. This makes the hair brittle and more likely to break, so you keep losing length and density.

How to Stimulate Hair Growth and Improve Overall Hair Health

Here are some tips to help you prevent hair loss and maintain healthier, stronger hair.

  • Go for a nutritious diet supported by nutrients or supplements that stimulate keratin production. This will encourage hair strength and growth. 
  • Balance your mental and physical health by adopting a regular workout regimen, hydrating, getting adequate sleep, and managing stress. 
  • Find a well-trained hair stylist and adopt safe hair styling methods. Similarly, avoid harsh hair products and use natural, organic ones whenever possible. 
  • Quit smoking. Smoking constricts blood vessels, which affects blood flow throughout the body, including the scalp. This reduced blood flow to the scalp minimizes nutrients reaching the follicles, which limits hair growth.
  • Trim your hair regularly. Yes, this seems counterproductive, but it works. Trimming hair gets rid of the split ends at the tips of your hair. Left untrimmed, these split ends lead to breakage. 
  • Avoid excessive heat styling, tight ponytails, braids, and other hairstyles that create too much tension on your scalp. The weakest hair on your head is your hairline. Pick hairdos that go easy on the hairline.

Hair Loss and How to Deal With It

It can be extremely frustrating when your hair keeps falling out despite your best efforts. And this can happen for many reasons, including:

  • Health conditions
  • Rapid weight loss
  • Lifestyle choices
  • Medications
  • Chronic stress
  • Hormonal imbalances
  • Poor styling and hair care practices

Despite the reasons behind the hair loss, losing chunks of hair can be devastating. The good news is that some types of hair loss can be reversed or slowed down. 

The first thing to do is find out why you are shedding too much hair and remedy that. For example, if you suspect a poor diet, smoking, or poor hair styling habits, reversing these can give your hair a better chance of recovering. 

The same goes for hair loss due to a drop in estrogen, which is common in women going through menopause. Here, you can discuss hormone replacement therapy with your doctor to balance out your hormones. Once this is taken care of, you get better control of hair growth as well. 

Broadly speaking, when your health is in good shape, so is your hair. So all the healthy habits you know of, including eating well, exercising, hydrating, not smoking, limiting alcohol intake, and so on, all support hair growth. This is an excellent place to start combating hair loss. 

There are also medications that can be used to slow down or stop hair loss and encourage new growth. The most common ones are:

  • Topical Minoxidil for male pattern baldness
  • Oral Finasteride
  • Antiandrogens
  • Low-level Laser therapy
  • Vitamin infusion therapy
  • Platelet-rich plasma therapy
  • Scalp micropigmentation
  • Forehead reduction surgery
  • Scalp Botox injections
  • Mesotherapy
  • Natural home remedies like rosemary oil, caffeine, and onion juice treatments

Still, while the above may deliver good results for thinning, they might not guarantee good results for severe hair loss. In this case, you can get the best outcomes from hair transplants.

Hair Transplants for Hair Loss

A hair transplant is a surgical procedure that takes hair from one part of your head to the thinning or balding areas. The hair to be transplanted is harvested from the area at the back of your head and from ear to ear. 

These hairs are resilient to most causes of balding, and they bring their sturdiness to the balding spots and continue to grow. 

The best thing about hair transplants is that if they are correctly done in patients not contraindicated for them, the results are almost guaranteed. The procedure takes a couple of hours, with about a week of recovery. 

You then begin to see new hairs by the 3rd month and a fuller head of hair by the one-year mark. The final results of a transplant are best assessed at 18 months following the procedure, and the results last a lifetime. 

Having Hair Trouble?

Hair speaks to our youthfulness, health, and vitality. As such, you lose more than just hair strands when your hair starts thinning or balding. 

At the Philadelphia Hair Restoration clinic, our sole job is to ensure clients regain their lustrous locks and keep them for as long as possible. With 18 years of experience, we can confidently guarantee seamless, successful procedures that leave you with hair to last a lifetime. 

No worries if you are bubbling with questions, either. Why not have an expert address your concerns? Talk to us today. 

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