What Is Hair Made Of?

What Is Hair Made Of?

What Is Hair Made Of? 

Your hair plays a key role in your unique look and style—but how much do you really know about the composition of your hair? Lucky for you, we’re here with the breakdown on what makes hair hair, and what you can do to keep yours happy and healthy.

Why Do We Even Have Hair?

Hair isn’t just for show, it serves a purpose, too. Our hair has several unique jobs that can differ depending on where it grows on the body. We’ve listed some of those key roles our hair can play:

  • Body hair helps to control our core temperature. Not only does it warm us up when we’re cold—think of goosebumps as your hair’s way of casting a wider net to trap more heat!—but it also helps our bodies to notice things touching it. Think of each hair as a motion sensor that detects bugs, parasites, and other creepy-crawlies that we might not notice on our skin!
  • Nasal hair works like an air filter, helping to keep germs from flying up our nose when we breathe.
  • Eyelashes work like another type of filter, this time catching dirt and dust that might otherwise fall into the eye and cause irritation or infection.
  • The hair on our head keeps us warm, but when well-maintained, it looks stylish and attractive, too!

Hair clearly wears many hats—pun intended!—by keeping us warm, alert, and, of course, fashionable.

The Composition of Hair

You’ve likely heard before that your hair is actually dead… What does that mean? When we run our hands through our hair, what we touch—the hair shaft—is actually made up of non-living cells that give the hair its rigid structure. At the base of the hair shaft inside the hair follicle is a different story, however, so let’s take a look at the major parts of what make up our glorious hair.

The Hair Follicle

Wanted or not, hair follicles—the tube-like structures in the epidermis, the skin’s outermost layer—blanket our body. Nearly five million hair follicles pockmark our skin, with roughly 100,000 calling the scalp their home. Below the skin’s surface is where the magic happens: Shafts of hair emerge upward from the dividing cells of the hair matrix, which shares the foundation of the follicle with dermal papilla cells inside the hair bulb.

Let’s break those parts down again, one at a time:

  • Dermal papilla cells are the core component of every hair follicle. They’re surrounded by blood vessels called capillaries, and the division of dermal papilla cells plays a part in how fast your hair grows, what stage of life your hair follicle is in, and more.
  • The germinal matrix sits above the dermal papilla, and new hair growth comes from germinal matrix cells as they divide and push upward through the skin. They also transfer color to the hair, known as pigmentation, by transferring melanin, the same compound that makes a mole on our skin look darker or gives us a tan when we’re out in the sun.
  • The hair bulb is the larger, round-shaped structure that includes the dermal papilla, germinal matrix, and the base of the growing hair shaft. It protects its contents and sits below the surface of the skin.
  • The sheath covers the outside of the growing hair shaft, giving it shape and structure. If the hair shaft is like a sword, think of the hair sheath as the holster for the sword that knights wear on their waists in those fantasy movies!
  • The sebaceous gland, closer to the skin’s surface, produces oil that lubricates our hair as it grows out. Sebaceous glands are everywhere, too—We’re all familiar with clogged sebaceous glands that lead to unwanted pimples and acne!
  • The arrector pili is a tiny muscle that contracts, or tightens, to make our hair stand up. Think goosebumps!

The Hair Shaft

What we consider to be a piece or strand of hair is called the hair shaft, and it contains several types of cells in three distinct layers.

  • The inner layer, or the medulla, is the core component of the hair shaft. It’s primarily made up of keratin, a protein that keeps hair strong and gives it structure.
  • The middle layer, or the cortex, surrounds the medulla as a layer of protection and support. Also primarily made of keratin, the cortex makes up most of the hair shaft itself.
  • The outer layer, or the cuticle, wraps around the cortex and is the outermost part that we actually touch. Think of the cuticle like protective bark on a tree: The abundance of keratin in the cuticle forms a rougher, scale-like surface that shields the more fragile inner layers.

How Does Hair Grow?

Now that we’ve broken down hair structure, let’s talk about how hair grows. Though we might think our hair is continuously growing, our follicles actually cycle between three major phases before each hair is naturally shed and a new one takes root in its place. Let’s take a look at what happens during each phase:

Anagen Phase

Lasting between 2-7 years for each follicle, roughly 85-90% of the hairs on our head are in anagen phase at any second! During the anagen phase, our matrix cells are hard at work, dividing every 18 hours or so to push the hair strand up, up, and away through the skin. While in this phase, our hair grows roughly half a millimeter each day.

The length of time that our hair follicles spend in anagen phase determines how long our hair is able to grow. For example, a hair follicle on our head may spend 2-7 years in anagen phase, allowing the hair shaft to grow very long. In comparison, however, the hair follicles that produce eyelashes, eyebrows, and body hair are much shorter, keeping the hairs produced in each much shorter than the hairs on our head.

Catagen Phase

In contrast to anagen phase, catagen phase takes up a literal hair of the hair’s lifespan, lasting 2-3 weeks on average. Because the phase is much shorter, fewer of our hairs are normally in the catagen phase at any given time. Think of our hair’s growth cycle as a roulette wheel with three pockets, where the size of each phase’s pocket is determined by the length of time the hair spends in that particular phase!

While hair growth still occurs during the catagen phase, it begins to slow down: By the end of this phase, hair stops growing altogether, becoming what’s known as club hair. Catagen phase represents the transition to the following period of rest, known as…

Telogen Phase

Telogen phase represents the part of the growth cycle when your hair rests and resets. Believe it or not, 10-15% of your hair follicles sit dormant on your dome in telogen phase for 2-4 months at a time! Once this brief hibernation is complete—and as long as the follicle remains in the land of the living!—the follicle can cycle back to anagen phase, push out the old hair shaft, and begin anew. Beautiful, isn’t it?

At the same time, the telogen phase plays a large part in hair loss, as well. Remember the roulette wheel we mentioned earlier? If each hair follicle begins to spend more time sitting around in the telogen phase, not only does that mean less time for growth: As the size of that roulette pocket increases, more and more hair follicles will appear to sync up and enter the resting phase at the same time. When this happens, it can lead to visible thinning on certain parts of the scalp. Something like stress can play a large role in changing the length of each hair follicle’s phase, and this is how temporary stress can lead to apparent temporary hair thinning and hair loss!

Keeping Your Hair Healthy

While our hair naturally goes through each of these three phases of growth over time, that doesn’t mean our choices don’t play a big part in how our hair goes through the growth cycle. Taking care of our hair keeps it growing as healthily as possible. Take a look at a few key tips below that are worth following:

Eat a healthy, balanced diet. That means getting a variety of foods from different food groups, including high-quality carbohydrates, fats, and lean proteins.

Get enough dietary zinc. Zinc is one of the many minerals that support healthy hair, and hair loss can actually be a common symptom of a zinc deficiency. Ideal sources of dietary zinc include nuts, fruits, and vegetables.

Read the ingredient list when purchasing hair care products. Not all shampoos, conditioners, gels, or serums are created equal. Some hair products contain harsh chemicals—like artificial colors, fragrances, sulfates, or preservatives—that can irritate the scalp or dry our hair out. If you’re concerned about how hair care products are tested for safety and comfort, have no fear: At Revela, not only are we dedicated to ditching harmful, irritating additives, we’re committed to being 100% cruelty-free, too. That means no testing on our furry friends!

If possible, avoid using shampoo on a daily basis. Have you ever seen a commercial for dish soap that shows volunteers scrubbing oil-covered wildlife with soap to help clean them up after an oil spill? Shampoo works similarly to remove oils and wash them away. Sometimes when we sweat or have overactive sebaceous glands on our scalp, that’s a good thing! However, healthy hair needs to keep itself coated in natural oils that frequent shampooing might otherwise strip away. On the days you don’t shampoo, try rinsing with water and using conditioner before capping off your routine with our Hair Revival Serum.

What Causes Hair Loss?

Hair loss is more common than you think: The most common form of hair loss is androgenic alopecia, typically known as male or female pattern hair loss, and it can affect nearly 25 percent of women over the age of 50. Though androgenic alopecia becomes more likely as we age, depending on factors like lifestyle and genetics, it can begin at a younger age, too.

The Causes of Androgenic Alopecia

Androgenic alopecia is primarily caused by an androgen—a male sex hormone—known as 5α-dihydrotestosterone (DHT). Despite the word androgen meaning “thing that makes us masculine”, androgens are present in both men and women, though in different amounts. Knowing the definition, you’ve probably already guessed that the hormone DHT plays an essential role in regulating the bodily changes we all experience during puberty!

Though both men and women have DHT, it’s probably not surprising that men possess higher levels of DHT than women—this also explains why androgenic alopecia tends to be more common in men than in women, as well.

Now let’s get science-y! DHT is a result of different androgen, testosterone, getting broken down into DHT. Testosterone levels tend to increase as we mature before plateauing in our 40s and declining throughout our golden years. Why the chemistry lesson? Well, when it comes to breaking down testosterone into DHT, a special enzyme, 5α-reductase, makes the magic happen—and it just so happens that outside of the male prostate, the scalp produces the highest amount of 5α-reductase in the body! 

It’s a complex signaling process, but DHT begins to cause hair follicles to constrict, making the hair shaft growing from the follicle emerge thinner, more fragile, and at a slower rate than before. More DHT means more shrinking follicles, and shrinking follicles equal thinner hair.

This is how DHT sabotages hair growth later in life, and because the enzyme that makes DHT from testosterone occurs more often in the scalp, it’s why we see baldness happen on our heads more often than elsewhere. If you didn’t know, now you know!

What Does Androgenic Alopecia Look Like?

In most cases, androgenic alopecia doesn’t result in complete and total baldness. Men and women who deal with this form of hair loss usually experience thinning and hair loss on certain predictable parts of the scalp.

For example, in men, androgenic alopecia typically results in the classic bald spot on the crown of the head, or thinning on either side of the forehead above the temples. In women, the thinning and hair loss often occurs where the hair is parted near the top of the head.

What Can I Do About Female Hair Loss?

Hair loss is always frustrating, but that doesn’t mean you have to give up hope. While it isn’t discussed as often as male pattern baldness, female hair loss is extremely common, and anyone experiencing it is far from alone!

If you’re concerned about avoiding hair loss, we’ve listed some key tips below to help you stay confident in your style and manage any noticeable thinning.

De-Stress for Healthier Hair

It’s no myth: Hair loss and stress are definitely connected. We mentioned above that stress can change the amount of time our hair follicle spends in the telogen phase, and that when more hair follicles are in this phase, thinning and hair loss can start to add up. This type of hair loss has a name: telogen effluvium, or “a flowing out [of hair] at the end of growth.”

Another common type of hair loss is alopecia areata, combining old Greek and Latin words to roughly mean “fur loss in an area.” Alopecia areata can occur anywhere on the body and it happens when our immune system attacks the hair follicle, damaging it in the process.

Stress can negatively affect both the signaling molecules in our body and our immune system. This means that a calmer, more peaceful mind can have an impact on the health of your hair!

Try implementing stress-reducing habits like yoga, meditation, or light exercise into your daily routine to keep stress levels at a minimum.

Talk to Your Doctor

For additional support in dealing with female hair loss, it never hurts to pay your doctor a visit. Specialists like dermatologists are usually best-equipped to handle your hair concern questions, but your primary care physician can check for underlying medical conditions first that might be impacting more than just your hair. If nutrient deficiencies or undetected medical conditions are to blame, a screening from your primary care provider is a great place to start for answers.

Use a Nourishing Hair Serum

It shouldn’t be hard to give your hair the nutrients it needs. Once you know what you’re looking for, choosing the right products for the results you need is easier than ever.

As we mentioned earlier, the dermal papilla cells deep in the hair follicle are the core component of every hair follicle. We tested real human follicle cells and used a computer algorithm to find never-before-seen ingredients that helped dermal papilla cells grow. Then we tested each ingredient to find the safest, most effective one.

That’s how we discovered ProCelinyl™.  At Revela, our Hair Revival Serum is uniquely formulated with this breakthrough ingredient. It targets those follicle cells to help them grow and divide effectively, while the supporting ingredients in our serum work to promote overall hair and scalp health, too.


We hope you’ve learned a bit more about how hair grows, what it’s made of, and how healthy habits can help to maintain even healthier hair. If you’re hoping to support healthy hair, try working the tips we’ve listed above into your daily routine—even better, work a little bit of our Hair Revival Serum into your roots, too! With a clinically tested formula that’s supported by dermatologists, your roots can finally get the reawakening they deserve.

Profile photo for Enzo Benfanti

Reviewed by: Enzo Benfanti, MEng

Enzo is a chemical engineer and data enthusiast with a background in industrial chemicals. His previous experience is in developing catalysts and designing industrial chemical processes to produce the precursors to detergents, polyester fibers, and other specialty materials. He received his bachelor’s degree from the University at Buffalo [Go Bills!] and his master's degree from Columbia University, both in chemical engineering.

Written by: Revela Editorial Team

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