How Do Hair Follicles Function?

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.

Hair growth cycle

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 2015 articleTrusted Source, 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 College of Dermatology, the average person loses approximately 100 strands of hair a day. About 90 percentTrusted Source of your hair follicles are in the anagen phase at any given time.

The life of a follicle

On average, your hair grows about half an inch each month. 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.

Issues with hair follicles

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 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.