Hair Follicle: Function, Structure & Associated Conditions

Hair Follicle

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Overview

What is a hair follicle?

A hair follicle is a tube-like structure (pore) that surrounds the root and strand of a hair. Hair follicles exist in the top two layers of your skin. You’re born with over 5 million hair follicles in your body and over one million hair follicles on your head. As you age, hair grows out of your hair follicles.

Your hair follicle is one of a few structures in your body that can stop functioning and begin functioning again (degenerate and regenerate). This process helps with hair growth on your body.

Function

What is the function of a hair follicle?

The function of a hair follicle is to grow your hair. In addition to promoting hair growth, your hair follicles do the following jobs:

• Help repair your skin after a wound or an injury.
• Form new blood vessels (angiogenesis).
• Form new nervous system neuron cells (neurogenesis).

How does a hair follicle help with wound healing?

The cells in your hair follicles help your body heal after a wound. When your body receives an injury, the cells within your hair follicles are closest to the wound and quickly move to the site of the wound to start the healing process. Your hair follicle cells assist your body’s white blood cells in your immune system.

How does hair grow out of a hair follicle?

Hair grows in cycles within your hair follicle:

• Anagen: The first phase of hair growth takes between two to seven years. Growth begins at the root (dermal papilla) in your hair follicle, which gives your hair blood supply and the nutrients it needs to grow. Your hair grows about 1 centimeter per month.
• Catagen: The second phase of hair growth occurs when the hair transitions from a growing phase to a resting phase, which takes about two weeks. During this phase, your hair detaches from your blood supply.
• Telogen: The final phase of hair growth is the inactive phase, where your hair sheds or falls out of your hair follicle. This phase takes up to four months.

Anatomy

Where are hair follicles located?

Wherever you have hair on your body, you also have hair follicles. Hair follicles originate in the first and second layers of your skin (epidermis and dermis). Follicles holding your terminal hair, or the hair that grows on your scalp, eyelashes and eyebrows, extend into the first and second layer of your skin and sometimes into the third layer (subcutaneous tissue).

What does a hair follicle look like?

A hair follicle looks like a long tube that holds your hair. It’s in the shape of a cylinder with a rounded bottom in your skin. The top of the cylinder is an open hole, which is where your hair grows out. Your follicle is similar to a sock; your hair is your foot that goes into your sock.

What does a hair follicle look like when it’s pulled out?

You can’t pull out a hair follicle, as it’s the structure within your skin that holds your hair. If you pull out a strand of hair, you might notice a bulb or round ball (root) attached to the end of the hair strand. The root is surrounded by nerve fibers that let you feel when your hair moves or you touch your hair. Removing this root doesn’t mean your hair won’t grow back, because in most cases, it will.

What color are hair follicles?

While your hair color can change throughout your life, your hair follicle, which is part of your skin, is the same color as your natural skin tone. The color of your hair follicle doesn’t relate to the color of your hair.

How big is a hair follicle?

The size of each hair follicle in your body is different based on the size of the cells that make up the base of the structure. Hair follicles are microscopic and you can’t see them simply by looking at your skin.

What is a hair follicle made of?

Your hair follicle is made up of layers of cells within layers of your skin. These cells create a tube-like structure to hold your hair.

Conditions and Disorders

What are the common conditions that affect hair follicles?

Several conditions affect the health of your hair follicles. The most common conditions include:

• Alopecia areata.
• Baldness in women and people assigned female and male at birth.
• Folliculitis.
• Hidradenitis suppurativa.
• Stress.
• Telogen effluvium.
• Whiteheads, blackheads or a dilated pore of Winer.

What are the symptoms of hair follicle conditions?

Symptoms vary for each condition and could include:

• Hair loss, thinning hair or limited hair growth.
• Pimples, fluid-filled bumps or blemishes on your skin.
• Swelling (inflammation).
• An itchy rash.
• A would that isn’t healing, has a yellow crust or leaks a white to yellow fluid (infection).

What tests check the health of my hair follicles?

Each condition requires different tests to make a diagnosis. Your healthcare provider will physically examine your skin and hair and ask questions about your medical history before running a test that could include:

• Blood test: Your provider will remove a small sample of your blood to check for conditions that cause your symptoms. Blood tests could include an ANA test, complete blood count (CBC), anemia test and c-reactive protein test.
• Biopsy: Your provider will remove a small sample of tissue from your skin to examine it under a microscope.
• Pull and tug test: Your provider will grab a small section of your hair and gently tug on it to identify how many strands fall out. They’ll perform this test on different sections of your hair on your head.

What are the common treatments for hair follicle conditions?

Treatment is unique to each person based on their symptoms and could include:

• Anti-inflammatory medicines like corticosteroids.
• Topical medicine (minoxidil) to help hair growth.
• Anti-itch medicines.
• Cleansers or creams that include salicylic acid, azelaic acid or benzoyl peroxide to remove blemishes.
• Antibiotics to clear bacteria or infections.
• Talking to a mental health professional to reduce stress.
• Hair transplant.

Care

How do I strengthen my hair follicles?

You can keep your hair follicles healthy and strong by taking care of your hair and your skin. You can do this by:

• Avoid pulling your hair out.
• Eating a healthy, well-balanced diet.
• Reducing stress.
• Wearing protective equipment like a helmet to avoid injury when participating in physical activities.
• Wearing sunscreen to protect your skin from the sun’s UV rays.
• Cleaning sores and practicing proper wound care if you have an injury.

Do hair follicles heal after an injury and will my hair grow back?

If you damage your hair follicles after an injury, they can repair themselves and your hair will grow back. It could take up to four years before you see new hair growth out of damaged hair follicles, depending on the severity of your injury. Frequent injuries to your skin and hair follicles can produce scars, which make growing hair difficult. Hair that does grow is thinner and more fragile hair than normal. This can lead to hair loss at the site of your injured skin.

A note from Cleveland Clinic

Hair follicles are part of your skin that are responsible for growing your hair. If you accidentally pull out a strand of your hair and it has a ball (bulb) on the end of it, you didn’t pull out the follicle, and instead, you removed your hair root. That root grows back and your hair will grow back, too. If you notice you’re not growing hair in an area that you used to grow hair, talk to your healthcare provider.

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