Have you ever looked in front of a mirror and noticed that your hair is not the same everywhere on your body? When you look at it, you realize that not all of our hair is the same. Think about it, there is a big difference between the thick hair on your head and the fine hair on your arms, right? That thick, often dark, strong hair is what we medically call 'terminal hair'. Although the name may sound a bit strange, this is the main type of hair on our body. So today we will talk about it all, very simply, in a way that you can understand.
So what exactly is terminal hair?
Simply put, terminal hair is the type of hair that is thick, visible, like the hair on your head, your eyebrows, and your eyelashes. When we are all born, we have very fine, thin hair on most of our bodies. But as we grow older, especially after puberty , those fine hairs on some parts of our bodies become terminal hair.
For example, hair begins to grow in places like the armpits and private parts. In boys, hair also begins to grow on the beard, chest, and stomach. On average, about 30% of a woman's body is covered with terminal hair. However, a man's body may be covered with this hair as much as 90%.
What is the difference between 'Terminal Hair' and 'Vellus Hair'?
As we mentioned earlier, the fine, thin hairs on our bodies are what we call 'Vellus Hair'. Some people also call this "peach fuzz". These are the type of hairs that we have all over our bodies when we are young. As we reach puberty, some of these turn into terminal hair. Let's look at the difference between the two in more detail.
| Characteristic | Terminal Hair | Vellus Hair |
|---|---|---|
| Thickness | Thick, strong hair. | A very fine, thin hair. |
| Color | Usually dark in color (black, brown). | Most of the time it is light in color, sometimes almost colorless. |
| Length | Too long. (Ex: hair on the head) | Short. |
| Skin location | It has roots deep within the skin. | It is connected to the surface layers of the skin. |
Why is this terminal hair important to our body?
This hair provides protection to our body in various ways.
- Body temperature control: Imagine your hair standing up on a cold day, right? We call it "standing up." This happens when a small muscle at the base of the hair shaft contracts. The hair shaft then stands up. When this happens, a layer of air heated by our body heat is trapped close to the skin. This keeps our body warm.
- Sun Protection: The thick hair on our heads protects us from the harsh rays of the sun that hit our scalp directly. It's like a natural hat.
- Protection from dust and dirt: Eyebrows and eyelids prevent sweat and dust from entering our eyes. Hair in the nose and ears also help stop germs and dirt from entering.
How is a hair shaft actually formed?
We only see the hair shaft that is visible above the skin. But underneath the skin, there is a complex structure. Each hair shaft has two parts. The part that is visible above the skin is called the hair shaft . The part that is embedded within the skin is called the hair root .
This hair root is surrounded by a small sac-like part of the skin. It is called a hair follicle . The root of each hair follicle is round like a small bulb. It is called a hair bulb . It is inside this bulb that the hair shaft receives the blood and nutrition it needs.
Our Hair Growth Cycle
Our hair doesn't grow all the time. It happens in a cycle. There are three main stages to this cycle. It's like a plant growing, growing for a while, dying, and then a new plant growing in its place.
| Stage | What is happening? | Time |
|---|---|---|
| 1. Growth Phase (Anagen Phase) | During this time, the hair shaft is actively growing. New cells are formed and pushed up the hair shaft. | This is the longest period. For a hair on the head, this period can be several years. But for an eyebrow, this period is as short as 100-150 days. That is why, while the hair on the head grows long, the eyebrow does not grow long. |
| 2. Transition Phase (Catagen Phase) | The hair follicle stops growing. The hair follicle begins to separate from the part that nourishes it. | This is a very short period of time, about 2-4 weeks. |
| 3. Resting Phase (Telogen Phase) | The blood supply to the hair follicle is completely cut off, and it becomes a completely "dead" hair follicle. These hair follicles gradually rise above the skin and fall out when we comb our hair or bathe. | This period can last for several months. After this hair falls out, a new hair begins to grow from the same follicle. The cycle begins again. |
It's normal to lose about 100 hairs from our heads a day. These are hairs that have entered the resting phase. There's nothing to worry about.
What is hair made of? How is color formed?
Our hair is mostly made up of dead cells filled with a protein called keratin . As the hair shaft reaches the surface of the skin, its cells lose their blood supply and die. Those dead cells fill with this protein called keratin.
Hair color is determined by the amount of a pigment called melanin . This is the same pigment that gives color to our skin. The more melanin there is, the darker the hair becomes. The less it is, the browner and goldener it becomes.
As we age, our body gradually reduces the production of this melanin. Then, spaces form inside the hair shaft, which are filled with air. That's when the hair shaft loses its color and looks white. When the black hair on the head and the new white hair combine, our hair looks gray.
Diseases and problems affecting terminal hair
Sometimes, various problems can arise with this terminal hair. Some people lose a lot of hair, while others have unwanted hair growth. Let's look at some of the main conditions.
Alopecia - that means hair loss
In medical terms, hair loss is called alopecia. This condition occurs when new hair follicles do not grow to replace the hairs that fall out. There can be many reasons for this.
- Hormonal imbalances
- Some medications
- Immune system problems (Autoimmune diseases)
Alopecia Areata
This is a problem with the immune system. What happens here is that our own body's defense cells attack our own hair follicles. This causes hair to fall out in patches. Sometimes hair can fall out anywhere on the body. Some people only lose hair in patches, while others can lose their hair completely. There are various treatments for this.
Androgenetic Alopecia
This is the most common type of baldness that is hereditary. In this condition, a hormone called dihydrotestosterone (DHT) damages the hair follicles. The follicles then shrink, the hairs that grow from them become thinner, shorter, and eventually stop growing altogether.
- Male Pattern Baldness: In this, hair begins to fall out from the sides of the forehead and the top of the head.
- Female Pattern Hair Loss: In most cases, women experience thinning hair on the top of their head, rather than balding. There is less hair loss in the front.
If you have a hair problem like this, the best thing to do is see your doctor to find out the exact cause and get the appropriate treatment.
Hirsutism - unwanted hair growth in women
This condition occurs in women. Here, like men, thick terminal hair begins to grow in places like the beard, chest, and stomach. The main reason for this is the excessive production of the male hormone androgen in the body. This condition is common in women with a hormonal problem called Polycystic Ovary Syndrome (PCOS) . There are various treatments for this, including hormone-regulating medications.
Hypertrichosis
This also causes excessive body hair growth. But unlike hirsutism, this is not caused by hormones. It can also affect both men and women. It can occur as a side effect of certain medications. In most cases, this condition goes away once the medication is stopped.
If you are experiencing hair loss or unwanted hair growth, please consult a qualified physician rather than trying things you find on the internet or hearsay, as these may be symptoms of an underlying medical condition.
Take-Home Message
- Terminal hair refers to the thick, dark hair found on our scalp and in places like our eyebrows.
- This hair performs several important functions, such as keeping our body warm and protecting it from the sun.
- Each of our hairs grows and sheds according to a three-phase cycle: growth, transition, and rest.
- Hormonal changes like puberty directly affect the growth of hair on our body.
- If hair loss is excessive or women experience unwanted hair growth, it could be a sign of a medical condition. Therefore, it is very important to seek medical advice.
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