Terminal Hair

What is terminal hair?

Terminal hair is the thick, coarse hair that grows on your scalp and makes up your eyelashes and eyebrows. After puberty, terminal hair may also grow on your face, armpits, pubic area, chest and belly (abdomen). Terminal hair covers about 30% of your body’s surface in people assigned female at birth. It covers about 90% of your body’s surface in people assigned male at birth.

What’s the difference between vellus hair and terminal hair?

Vellus hair is the fine, thin hair that grows all over your body. You may call vellus hair “peach fuzz.” Vellus hair is the type of hair that develops on your body during childhood. After puberty, some vellus hair turns into terminal hair.

You may have vellus hair on your face, neck, arms, legs and chest. Vellus hair is usually shorter and lighter than terminal hair. Terminal hair is usually longer and darker. Also, terminal hair extends deeper into your skin than vellus hair.

What’s the purpose of terminal hair?

Terminal hair protects your body in different ways. Your terminal body hair helps control your body’s temperature. When you’re exposed to cold temperatures, the hair on your body stands up. This keeps air that’s been warmed by your body close to your body to keep you warm.

In addition, the hair on your head protects your scalp from the sun’s damaging rays. Your eyebrows and eyelashes help keep sweat, dirt and dust out of your eyes. Hairs in your ears and nose help keep germs out too.

Where is terminal hair located?

You have terminal hair all over your body. This may include your:

• Head (scalp).
• Armpits.
• Pubic area.
• Upper lip, cheeks and chin.
• Eyelashes and eyebrows.
• Chest and belly (abdomen).
• Back.
• Arms and legs.
• Fingers and toes.

What is the structure of terminal hair?

You see the terminal hair that’s on the outside of your body. But underneath your skin is a complex hair structure. Each one of your hairs has a hair shaft and a hair root. The hair shaft is the part you can see — the part that sticks out of your skin. The hair root extends deep down within the layers of your skin.

A sheath of skin and connective tissue called the hair follicle surrounds each hair root. Each hair follicle is attached to a tiny muscle that makes your hair stand up. At the base of each hair, the hair root widens into a round hair bulb. At the bottom of the hair bulb is the hair papilla. The hair papilla supplies your hair root with blood.

How does terminal hair grow?

In each hair bulb, new hair cells are constantly forming. These cells stick together and harden, and a full strand of hair develops. New hardened cells attach to the hair from below, which gradually pushes your hair up and out of your skin. Each hair on your head grows at a rate of about 1 centimeter each month. Body hair and facial hair grow slower.

What is the growth cycle of terminal hair?

Your hair grows in three phases and then starts again.

Growth phase

The growth phase or anagen phase is the first phase of the growth cycle. This is when your hair is actively growing. As long as you continue to develop new hair cells, your hair will continue to grow. The place on your body determines the terminal hair length. For example, the terminal hair on your head can grow for several years, so it can grow to more than a meter in length. But your eyebrow and eyelash hairs have a shorter growth phase. They only grow for 100 to 150 days, so they can’t grow as long.

Transitional phase

The transitional phase or catagen phase is the second phase of the growth cycle. At the end of the growth phase, your hair root starts to separates from its papilla. The transitional phase is the shortest phase in the hair growth cycle. This phase usually only takes two to four weeks.

Resting phase

The resting phase or telogen phase is the third and final phase of the growth cycle. After your hair has completely separated from its papilla, its blood supply is cut off. The hair is slowly pushed up out of your skin and eventually falls out. The resting phase can take several months.

Then, new hair cells form in your hair follicles to create new hairs, and the cycle starts again.

What is terminal hair made of?

Dead hair cells filled with a protein called keratin make up most of your terminal hair. As your hair grows toward the surface of your skin, the blood supply to its hair cell is cut off and the cell dies. At the same time, the part that sticks out of your head (the hair shaft) undergoes a process called keratinization. During keratinization, your hair shaft fills with keratin. Your hair is made up of a mix of this keratin and the cells that died during the normal growth process.

How is the color of terminal hair determined?

The amount of pigment (melanin) in your hardened hair cells determines the color of your hair. As you get older, the amount of melanin usually decreases. When melanin decreases, air gets trapped inside your hair. When this happens, your hair loses its color and it turns white. Depending on your original hair color and the number of white hairs that grow, the hair on your head then turns gray or white.

What happens with terminal hair during puberty?

During puberty, your hormone levels begin to rise. Your body’s endocrine system produces more of a hormone called androgens. The increase causes vellus hair on some parts of your body to turn into terminal hair. In both people assigned male at birth (AMAB) and people assigned female at birth (AFAB), vellus hair in the armpits and pubic area turns into terminal hair.

When some people AMAB (and some people AFAB) go through puberty, vellus hair on the upper lip, cheeks and chin turns into terminal hair. Terminal hair also grows longer on your upper back, chest, knuckles, arms and legs.

What conditions and disorders can affect terminal hair?

Several conditions can cause excessive terminal hair growth or terminal hair loss.

Alopecia

The average person loses about 100 hairs each day. But as you get older, your hair growth rate decreases. In addition, if you have damage to your hair roots during the growth phase or a lot of hairs go into the resting phase at the same time, you may experience hair loss (alopecia).

Alopecia is a condition that occurs when no new hair grows to replace those hairs. There are several types of alopecia. In some types of alopecia, the hair can grow back. Alopecia is a common condition with many causes. Other causes of alopecia include:

• Autoimmune diseases.
• Certain medications.
• Hormonal imbalance.

Alopecia areata

Alopecia areata is an autoimmune disease. The disease causes your immune system to attack your body. The condition causes your hair to fall out in large clumps. Alopecia areata can affect the hair anywhere on your body. But it most commonly affects the hair on your head. The amount of hair loss can vary. Sometimes, it’s only in a few spots. Other times, you may have total hair loss. Treatment options may include the use of an anti-inflammatory such as a corticosteroid or a topical solution such as minoxidil (Rogaine®).

Androgenetic alopecia

Androgenetic alopecia is a genetic condition that causes gradual hair loss on your scalp after puberty. The condition occurs when a type of androgen called dihydrotestosterone (DHT) damages your hair follicles. The follicles shrink and start producing shorter, thinner vellus-like hair. Treatment for androgenetic alopecia includes medications including topical minoxidil and finasteride (Propecia®). Androgenetic alopecia affects both people AMAB and people AFAB:

• Male pattern baldness: Male pattern baldness is androgenetic alopecia that affects people AMAB. Hair loss most commonly occurs around the crown and frontal hairline. You may hear the term receding hairline.
• Female pattern hair loss (FPHL): Female pattern hair loss (FPHL) is androgenetic alopecia that affects people AFAB. Hair loss occurs around the crown and top of your head but doesn’t affect your frontal hairline. You may notice a wider center part.

Hirsutism

Hormonal imbalance during the reproductive years of people AFAB can lead to hair growth disorders such as hirsutism. Hirsutism causes excess terminal hair to grow in people AFAB in a pattern typically seen in people AMAB. The condition occurs due to an excess of androgen. The most common cause of hirsutism is a hormonal disorder called polycystic ovary syndrome (PCOS). Treatment options include hair removal and hormonal medications such as oral contraceptives.

Hypertrichosis

Hypertrichosis is excessive hair growth anywhere on your body that’s not caused by an excess amount of androgen. It’s usually the result of certain medications. Sometimes certain disorders can lead to the condition as well. It can affect people AMAB and people AFAB. Treatment usually includes laser hair removal, depilatory creams and/or electrolysis. Often, if you stop taking the medication causing the condition, it can help reverse your symptoms.

What is a terminal hair cyst?

A terminal hair cyst is a rare type of epidermoid cyst. An epidermoid cyst is a small lump filled with keratin that develops under your skin. A terminal hair cyst is a brownish-black or blue-colored bump in your skin. It may have a pore-like opening on the surface. These types of cysts are most commonly found on your head or neck. They are usually noncancerous (benign).