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Hair Follicle: Understanding Function, Structure, and Common Conditions

Knox Beasley, MD

Reviewed by Knox Beasley, MD

Written by Lauren Panoff

Published 05/14/2022

Updated 12/08/2024

There are millions of hair follicles all over your body — but can you describe how hair follicles look or what they do?

We’ll start with the basics: Hair follicles are tiny but complex structures located inside your skin. They play a critical role in hair growth and they help heal tissue and keep skin naturally moisturized.

Healthy hair follicles are essential not just for a full head of hair, but also for smooth and healthy skin.

Contrary to popular belief, hair follicles can’t be pulled out — though they can be damaged. Damaged hair follicles lead to hair loss and male pattern baldness, which is why healthy hair starts with healthy follicles.

Below, we cover exactly what hair follicles are and how they function. We also get into the nitty gritty of how certain conditions affect hair follicles and what you can do about them.

A hair follicle is a tiny structure, sometimes referred to as a “mini-organ” that’s found within your skin.

While they’re associated with growing hair, hair follicles do so much more than just that.

The different parts of each hair follicle work together to carry out the following functions:

  • Facilitating hair growth

  • Producing sebum, the natural oil that keeps your skin moisturized and healthy

  • Forming nerve endings and sensitive touch receptors

  • Forming new blood vessels

  • Acting as a temperature regulator by generating heat when you get cold

  • Helping your skin heal after injury

The human hair follicle is a Jack of many trades.

Hair Follicle Function

Your hair follicles are hard at work promoting hair growth, forming new blood vessels and nerve cells, and even helping to repair wounded skin. So, how does a hair follicle carry out its functions? 

The hair follicle is like a tiny underground factory of your scalp, diligently producing each strand of hair. Deep in the skin, the follicle houses the root of each hair, providing it with essential nutrients.

At the base, there's the hair bulb, where cells multiply like they’re at an all-you-can-grow buffet, creating the hair shaft that pushes upward. 

Along the way, the follicle gets a little help from the sebaceous gland, adding a touch of natural oil to keep everything looking smooth and shiny. 

All in all, your hair follicle is the hardworking hero of what appears on your head, cranking out new growth day after day.

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To the naked eye, hair follicles might not look that interesting — the “pores” are tiny dot-like structures with hairs in them.

But if you look at a cross-section of a human hair follicle, there’s actually a lot going on.

Hair follicles are long, cylinder-shaped holes in your skin. Your hair shaft starts growing from the bottom of the follicle, which keeps the shaft firmly in place until it falls out.

Inside the hair follicle, there’s:

  • A sebaceous gland, which produces and secretes sebum (that oil we mentioned)

  • An arrector pili muscle (or hair erector), which helps your hair shaft “stand up” when you’re cold

  • The hair root (dermal papilla), out of which your hair will grow

  • A hair bulb, which is connected to a melanocyte (a mature melanin-forming cell)

  • An outer root sheath, which is a tissue made up of undifferentiated keratinocytes  (keratin-producing cells)

The structure is set deep in your skin, with the hair root starting in the subcutaneous layer. It extends into the dermis and epidermis (quick health class reminder: the epidermal layer is the surface layer of your skin).

Your hair begins its life cycle in the hair bulb. In a process called differentiation, hair follicle stem cells form three different layers of each hair strand:

  • The medulla, or center layer

  • The cortex, or middle layer

  • The cuticle, or outermost layer, which secures the shaft to the follicle

Hair follicles also determine your hair type and appearance. The shape of the follicle determines how curly or straight your hair is, while the melanin content determines your hair color. The melanin pigment comes from the melanocyte in the hair bulb.

As you age, your ability to produce melanin decreases. This is why your hair might turn gray or white over time.

Dead and Damaged Hair Follicles

You might be wondering, okay, but what do dead hair follicles look like? Dead hair follicles often appear as small, smooth areas on the scalp or skin where hair no longer grows. Your skin might be slightly shiny or thinner compared to the surrounding skin. 

If a hair follicle is completely dead, no new hair will grow from it, and eventually, the follicle may shrink or even close up. In some cases, you may also see tiny, closed pores where the hair used to be, but without visible hair shafts or stubble.

If you have a damaged hair follicle — but it’s not dead — they may still produce hair, but it may not look quite right. Hairs from damaged follicles often have weakened growth that makes them appear thin or uneven. 

This might be caused by things like chemical treatments, high-heat tools, or underlying inflammation that contributes to weakened follicles. Over time, damaged hair follicles might eventually lead to hair loss if not treated. 

Before we get into the secondary functions of your hair follicles, let’s discuss the most significant one: growing hair.

Hair follicles are found everywhere from your scalp and face to your armpits, genitals and buttocks, and even the insides of your nose and ears. Even areas without any visible hairs, such as your earlobes and forehead, contain hair follicles.

The Hair Growth Cycle

Every hair on your body grows the same way.

Hair cells are mostly produced from keratin during keratinization.

The growth process involves multiple phases, during which a hair shaft (the visible part of your hair that you can see and touch) grows out from the hair bulb inside the hair follicle.

The hair follicle cycles through three phases:

  • The anagen phase (also called the proliferation or growth phase). During this phase, the hair follicle actively produces a new hair shaft. Epithelial stem cells stimulate the growth of hair downwards, creating a hair bulb, which then grows upward and breaks through the skin. Scalp hair follicles typically spend two to six years in the anagen phase, while hair follicles in other areas of your body may only spend a few months in this phase.

  • The catagen phase (or transition phase). During the catagen transition, cell division inside the hair matrix stops, and your hair goes from active growth to regression. It becomes a “club hair” with a small white node at its end.

  • The telogen phase (or resting phase). Hairs that are in the telogen phase no longer actively grow, but remain attached to the follicle until they shed. Scalp hairs stay on the scalp for around 100 days before shedding.

Some experts include the shedding period — or the exogen phase — as a fourth distinct phase in the hair cycle. This is, of course, when the hair falls out. The American Osteopathic College of Dermatology estimates that most healthy people lose around 100 hair strands a day.

After hair falls out, the growth cycle starts again, and a new hair shaft grows from the follicle.

At any given time, between 85 and 95 percent of your hair follicles will typically be in the anagen phase of the hair growth cycle. This allows your hair to continuously grow, with new hairs replacing old ones as they shed and re-enter the cycle.

Our full guide to the hair growth cycle provides more information about how your hair grows and sheds, as well as the impact that the hair follicle cycle can have on your hair’s thickness and overall appearance.

Hair Follicles and Sebum Production

Through the attached sebaceous gland, each hair follicle in your skin also plays a key role in the production of sebum —a type of natural oil that keeps your skin moisturized and healthy.

In fact, the sebum produced by your sebaceous glands accounts for around 90 percent of the lipids that lubricate and protect your skin surface.

After sebum is produced, it empties in the follicular canal and then travels to the outermost layer of your skin.

But sebum does more than lubricate your skin. It also creates a physical barrier that provides protection against bacteria, fungi and other potential sources of infection.

This is one reason you may notice that your skin tends to feel oilier in the areas of your body with lots of hair.

Unfortunately, sebum can also cause certain problems. For example, when your sebaceous glands release too much sebum, it can mix with dead skin cells and pollutants. This produces sebum plugs in your hair follicles, resulting in acne.

Hair Follicles and Heat

Your hair follicles don’t just grow hairs and secrete sebum — they also play a vital role in keeping your body warm.

A small muscle called the arrector pili muscle can be found at the base of each human hair follicle. If your body temperature starts to drop, these muscles all contract at the same time in order to produce heat throughout your skin tissue.

This muscle contraction is what causes your hair to “stand up straight” when you spend time in a cold environment.

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A hair follicle can’t be “pulled out,” but it can be damaged. And when a hair follicle is damaged, it can’t carry out its functions — including growing hair.

Let’s go over the types of hair loss conditions that can affect hair follicles.

Male Pattern Baldness

Male pattern baldness, also referred to as androgenetic alopecia, is the most common form of hair loss in men. It’s responsible for receding hairlines and bald spots around the crown.

This type of hair loss occurs when your hair follicles are damaged by an androgen (male hormone) called dihydrotestosterone (DHT). Over time, DHT shrinks your hair follicles, making it impossible for them to grow viable new hairs and resulting in visible hair loss.

For the most part, male pattern baldness is a genetic issue. Research suggests that people with this type of hair loss have above-average levels of DHT, as well as greater levels of sensitivity to the effects of DHT in the scalp.

Traction Alopecia

Tight hairstyles — think restrictive ponytails, man buns, or cornrows — can put pressure on your scalp and pull at your hair follicles. Over time, this can damage your follicles to the point where they can’t produce hair any more.

If you treat traction alopecia in the early stages, it can be reversed. But long-term traction alopecia can potentially cause scarring and often results in permanent hair loss.

The best way to treat — or better yet, prevent — traction alopecia is to avoid putting pressure on your hair follicles. Opt for gentle styling habits and looser hairstyles.

Tinea Capitis

Also known as scalp ringworm, tinea capitis is a fungal infection that can affect your scalp hair follicles, potentially leading to hair loss.

Sometimes, the hair loss from tinea capitis is only temporary. But if it causes inflammation, it can lead to permanent hair loss. It can also affect the hair follicles on the rest of your body, including the eyebrows and eyelashes.

Tinea capitis is usually treated with antifungal medications or shampoos.

Cicatricial Alopecia (Scarring Alopecia)

Scarring alopecia is an inflammatory hair loss that causes permanent damage to your hair follicles.

There are two main types of cicatricial alopecia:

  • Primary cicatricial alopecia, which is caused by inflammation that develops beneath the skin’s surface, possibly instigated by a bacterial or fungal infection (like tinea capitis).

  • Secondary cicatricial alopecia, which is caused when an external injury or damage — like a tumor or burn — hurts your hair follicles.

In both cases, the hair follicles are replaced by scar tissue. This causes permanent hair loss in the affected area of the scalp.

Alopecia Areata

An autoimmune condition, alopecia areata occurs when your immune system targets and attacks your hair follicles. This causes your hair to fall out in patches, sometimes across your scalp and the rest of your body.

In some cases, alopecia areata can be treated — especially when caught early — meaning it doesn’t have to result in permanent hair loss.

Folliculitis

Folliculitis doesn’t cause hair loss, but it can be extremely uncomfortable. With folliculitis, your follicles will become inflamed, causing numerous small bumps to appear on your skin. These bumps are often itchy and sore.

Folliculitis can occur anywhere hair grows on your body, from your scalp to your armpits, stomach, and groin.

Sometimes, folliculitis is caused by a staph infection or another bacterial infection. It can be treated with oral or topical medications.

Our bodies have a pretty incredible ability to give us signs that something isn’t quite right, but we have to pay attention to notice and pick up on these signals.

While symptoms of hair follicle issues can vary and be nonspecific, here are a few things that could indicate something that needs a closer look:

  • Redness and inflammation: The affected area may appear irritated, with noticeable swelling or redness around the follicles.

  • Pain or tenderness: You may experience discomfort or soreness, especially when touching or brushing your hair.

  • Pimple-like bumps: Small white or red bumps can form around the follicles, resembling acne.

  • Itching or irritation: Persistent itching can occur, sometimes worsening when exposed to heat or sweat.

  • Hair thinning or loss: Hair may fall out more easily or in patches, indicating a disrupted growth cycle.

  • Pus or fluid drainage: In severe cases, infected follicles may ooze pus or fluid, signaling infection.

Testing for Hair Follicle Health

If you suspect a hair follicle issue, several tests can help diagnose the problem and assess the health of your follicles. Here's how some common methods work:

  • Scalp examination: A dermatologist will visually inspect your scalp for signs of inflammation, irritation, or infection. Patterns of hair loss or thinning, bumps, redness, and scaling can indicate a problem.

  • Pull test: During this simple test, a healthcare provider will gently tug on small sections of hair to see how easily it comes out. If a large number of hairs come loose, it could indicate issues like telogen effluvium or hair follicle damage.

  • Scalp biopsy: If more information is needed, a small piece of scalp tissue may be removed (called a biopsy) for closer examination under a microscope. This can help identify conditions like alopecia areata, scarring alopecia, or folliculitis.

  • Trichoscopy: This is a non-invasive technique that uses a special magnifying device to closely examine the hair and scalp. It helps detect structural abnormalities in the hair shafts or follicles, as well as early signs of scalp diseases.

  • Blood tests: If an internal issue like a hormone imbalance or nutrient deficiency is suspected, blood tests can check for conditions that affect hair health, such as thyroid problems, iron deficiency, or autoimmune disorders.

These tests can help pinpoint the root cause of hair follicle problems, allowing for more targeted treatment to restore scalp health and promote hair growth.

Not all hair follicle conditions can be treated, but certain hair loss treatments can stimulate hair follicles and prevent further hair loss.

Your healthcare provider will be best equipped to determine what kind of treatment is best for your specific type of hair loss. They might recommend:

Future hair loss treatments might include stem cell therapy, where hair follicle stem cells are used to help regenerate damaged follicles.

Of course, not all hair loss treatments are suitable for all types of hair loss. The treatment you choose will depend on your exact needs. Again, a healthcare practitioner can diagnose your follicle condition and help you figure out the best treatment for you.

The best way to address hair follicle issues and hair loss is to prevent them in the first place. While that’s not always possible, of course, everyday habits can make a significant difference over time. 

Here are some tips to help strengthen your hair follicles and promote healthier hair:

  • Maintain a balanced diet: Include nutrient-rich foods like leafy greens, nuts, seeds, and lean proteins (e.g., legumes, nuts, seeds, poultry, fish) to provide your follicles with essential vitamins and minerals like biotin, zinc, and iron.

  • Scalp massages: Regular scalp massages can stimulate blood flow to hair follicles, improving nutrient delivery and promoting hair growth.

  • Use gentle hair care products: Choose sulfate-free shampoos and conditioners that are gentle on the scalp, avoiding harsh chemicals that may weaken follicles.

  • Avoid excessive heat styling: Minimize the use of high-heat styling tools like straighteners and blow dryers, which can damage hair follicles and cause breakage.

  • Keep your scalp clean: A healthy scalp supports strong follicles, so wash your hair regularly to remove dirt, oil, and product buildup that can clog follicles.

  • Stay hydrated: Drinking plenty of water helps keep both your scalp and hair hydrated, which is essential for healthy follicle function.

  • Manage stress levels: Chronic stress can disrupt the hair growth cycle and weaken follicles. We can’t always avoid stressors, but you can help improve your response to them through practices like meditation, yoga, listening to calming music, journaling, or taking a walk. 

  • Avoid tight hairstyles: Hairstyles that pull on the hair, such as ponytails or braids, can strain the follicles and lead to thinning or breakage. Keep your styles loose when possible.

Hair loss treatments, delivered

Your hair follicles are situated all over your skin. Understanding hair anatomy and follicle function can help you understand hair loss better.

  • Your hair follicles do more than just grow hair. They’re also involved in keeping your skin healthy and protected — and even keeping you warm as the temperature drops.

  • Many conditions can affect your hair follicles. Male pattern baldness, traction alopecia and tinea capitis — a fungal infection — can damage your follicles and cause hair loss.

  • But you may be able to treat it. Some hair loss conditions can be treated. Minoxidil and finasteride are two types of medications that can stimulate the follicles, reducing hair loss.

You can learn more about dealing with baldness and other types of hair loss in our guide to the best treatments for thinning hair.

Not sure where to start? A healthcare professional can diagnose the type of hair loss you have and help you understand your treatment options — and we can help connect you with a healthcare professional.

13 Sources

  1. American Osteopathic College of Dermatology. Telogen Effluvium Hair Loss. Retrieved from: https://www.aocd.org/page/TelogenEffluviumHA
  2. Ho CH, Sood T, Zito PM. (2024). Androgenetic Alopecia. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK430924/
  3. Hoover E, Aslam S, Krishnamurthy K. (2022). Physiology, Sebaceous Glands. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK499819/
  4. Hussein RS, Atia T, Bin Dayel S. (2023). Impact of Thyroid Dysfunction on Hair Disorders. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/37692605/
  5. Kuczara A, Waśkiel-Burnat A, Rakowska A, Olszewska M, Rudnicka L. (2024). Trichoscopy of Androgenetic Alopecia: A Systematic Review. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/38610726/
  6. Lin CS, Chan LY, Wang JH, Chang CH. (2023). Diagnosis and treatment of female alopecia: Focusing on the iron deficiency-related alopecia. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/38035053/
  7. Martel JL, Miao JH, Badri T, et al. (2024). Anatomy, Hair Follicle. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK470321/
  8. Medline Plus. (2023). Hair follicle anatomy. Retrieved from: https://medlineplus.gov/ency/imagepages/9703.htm
  9. Milner Y, etla. (2002). Exogen, shedding phase of the hair growth cycle: characterization of a mouse model published correction appears in J Invest Dermatol. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/12230507/
  10. Johns Hopkins. Anatomy of the Skin. Retrieved from: https://www.hopkinsmedicine.org/health/skin/anatomy-of-the-skin
  11. Schneider MR, Schmidt-Ullrich R, Paus R. (2009). The hair follicle as a dynamic miniorgan. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/19211055/
  12. Wolff H, Fischer TW, Blume-Peytavi U. (2016). The Diagnosis and Treatment of Hair and Scalp Diseases. Retrieved from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4908932/
  13. Winters RD, Mitchell M. (2024). Folliculitis. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK547754/
Editorial Standards

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Knox Beasley, MD

Dr. Knox Beasley is a board certified dermatologist specializing in hair loss. He completed his undergraduate studies at the United States Military Academy at West Point, NY, and subsequently attended medical school at Tulane University School of Medicine in New Orleans, LA. 

Dr. Beasley first began doing telemedicine during his dermatology residency in 2013 with the military, helping to diagnose dermatologic conditions in soldiers all over the world. 

Dr. Beasley is board certified by the American Board of Dermatology, and is a Fellow of the American Academy of Dermatology.

Originally from Nashville, TN, Dr. Beasley currently lives in North Carolina and enjoys spending time outdoors (with sunscreen of course) with his wife and two children in his spare time. 

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