Hair follicles are small, pocket-like holes in our skin. As the name suggests, they grow hair. The average human has about 100,000 hair follicles on the scalp alone, according to the American Academy of Dermatology. We’ll explore what hair follicles are and how they grow hair.

A hair follicle is a tunnel-shaped structure in the epidermis (outer layer) of the skin. Hair starts growing at the bottom of a hair follicle. The root of the hair is made up of protein cells and is nourished by blood from nearby blood vessels.

As more cells are created, the hair grows out of the skin and reaches the surface. Sebaceous glands near the hair follicles produce oil, which nourishes the hair and skin.

Hair grows out of the follicles in cycles. There are three different phases of this cycle:

  • Anagen (growth) phase. The hair begins to grow from the root. This phase usually lasts between three and seven years.
  • Catagen (transitional) phase. The growth slows down and the follicle shrinks in this phase. This lasts between two and four months.
  • Telogen (resting) phase. The old hair falls out and new hair begins to grow from the same hair follicle. This lasts between three and four months.

According to a , recent research has suggested that hair follicles aren’t just “resting”’ during the telogen phase. A lot of cellular activity happens during this phase so that the tissues can regenerate and grow more hair. In other words, the telogen phase is crucial to the formation of healthy hair.

Different follicles go through different phases of the cycle at the same time. Some follicles are in the growth phase while others might be in the resting phase. Some of your hairs might be growing, while others are falling out.

According to the American Osteopathic Academy of Dermatology, the average person loses approximately 100 strands of hair a day. About of your hair follicles are in the anagen phase at any given time.

On average, your hair grows about half an inch each year. Your hair growth rate can be affected by your age, hair type, and your overall health.

Hair follicles aren’t just responsible for how much your hair grows, they also influence what your hair looks like. The shape of your follicle determines how curly your hair is. Circular follicles produce straight hair while oval follicles produce curlier hair.

Hair follicles also play a part in determining the color of your hair. As with skin, your hair gets its pigment from the presence of melanin. There are two types of melanin: eumelanin and pheomelanin.

Your genes determine whether you have eumelanin or pheomelanin, as well as how much of each pigment you have. An abundance of eumelanin makes hair black, a moderate amount of eumelanin makes hair brown, and very little eumelanin makes hair blonde. Pheomelanin, on the other hand, makes hair red.

This melanin is stored in hair follicle cells, which then determine the color of the hair. Your follicles can lose their ability to produce melanin as you age, which results in the growth of gray or white hair.

If hair is pulled out of the hair follicle, it can regrow. It’s possible that a damaged follicle will stop producing hair. Certain conditions, such as alopecia, can cause follicles to stop producing hair altogether.

A number of hair conditions are caused by issues with hair follicles. If you think you have a hair condition, or if you have unexplained symptoms like hair loss, it’s best to consult with a dermatologist.

Androgenetic alopecia

Androgenetic alopecia, which is known as male pattern baldness when it presents in men, is a condition that affects the growth cycle of hair follicles on the scalp. The hair cycle slows down and weakens, eventually stopping altogether. This results in the follicles not producing any new hairs.

According to the U.S National Library of Medicine, 50 million men and 30 million women are affected by androgenetic alopecia.

Alopecia areata

Alopecia areata is an autoimmune disease. The immune system mistakes the hair follicles for foreign cells and attacks them. It often causes hair to fall out in clumps. It can lead to alopecia universalis, which is a total loss of hair all over the body.

No known cure exists for alopecia areata yet, but steroidal injections or topical treatments can slow down hair loss.

Folliculitis

Folliculitis is an inflammation of the hair follicles. It can occur anywhere hair grows, including your:

  • scalp
  • legs
  • armpits
  • face
  • arms

Folliculitis often looks like a rash of small bumps on your skin. The bumps may be red, white, or yellow and they can contain pus. Often, folliculitis is itchy and sore.

Folliculitis is often caused by a staph infection. Folliculitis can go away without treatment, but a doctor can diagnose you and give you medication to help manage it. This can include topical treatments or oral medications to treat the cause of the infection and soothe the symptoms.

Telogen effluvium

Telogen effluvium is a temporary, but common form of hair loss. A stressful event causes hair follicles to go into the telogen phase prematurely. This causes the hair to thin and fall out. The hair often falls out in patches on the scalp, but in extreme cases, it can fall out in other places on the body, including on the legs, eyebrows, and pubic region.

The stress could be caused by:

  • a physically traumatic event
  • childbirth
  • a new medication
  • surgery
  • illness
  • a stressful life change

The shock of the event triggers the change in the hair growth cycle.

Telogen effluvium is usually temporary and doesn’t require treatment. However, it’s best to speak to a dermatologist if you think you have telogen effluvium, because they’ll need to rule out other causes.

If you have conditions like alopecia or balding, you might wonder if it’s possible to stimulate a hair follicle to regrow hair.

If a follicle has been damaged, it’s not possible to restimulate it. At least, we don’t yet know how to restimulate it.

However, some new stem cell research provides hope. A found a new method of reactivating dead or damaged hair follicles. However, this treatment hasn’t yet been tested on humans and it hasn’t been approved by the Food and Drug Administration (FDA).

Your hair follicles are responsible for growing hair, which happens in cycles of three distinct phases. These follicles also determine your hair type.

When damaged, the follicles can stop producing hair, and your hair growth cycle can slow down. If you have any concerns about your hair growth, talk to a dermatologist.