Body hair

Most of your body has hair.

It is very soft and light. This hair is almost invisible.

As you grow up, your hair changes. Body parts like your arms get hairier. This hair becomes darker and thicker.

This change happens because of things in your body. These things make the hair grow more. It can happen on your chin or chest.

Some hair grows for a long time. Other hair grows for only a few months. This is why head hair is so long.

Body hair helps you feel the world. It can feel things moving in the air. It also feels tiny bugs on your skin.

Most of your body is covered in hair. Most of it is vellus hair. This hair is very fine and light. You can barely see it.

During puberty, your hair changes. This new hair is called terminal hair. It is darker and thicker. This happens because of androgens. These are male hormones in the body.

Androgens make hair grow more. They also make hair grow thicker. This change happens at different times. For example, pubic hair often grows first. This is because that area is very sensitive to hormones.

Body hair grows in a special way. Hair on your head stays long for years. This is called the anagen phase. But body hair has a short anagen phase. It only grows for a few months.

Body hair also helps you feel things. It can feel tiny bugs on your skin. It can even feel air moving. This is because the hair moves tiny nerves in your skin. This lets you feel the world around you.

Most people have two different types of hair on their bodies. The first kind is called vellus hair. This hair is very fine and light in color. It covers almost the entire body from childhood onward. You can find it on your arms, legs, and chest. It is hard to see unless you look very closely.

There are a few places where this hair does not grow. These places include your palms, the soles of your feet, and your lips.

During puberty, a second kind of hair begins to grow. This is called terminal hair, or androgenic hair. It is much darker and thicker than vellus hair. This change happens because of androgens. Androgens are hormones that act as signals in the body. For the hair to grow, these hormones must reach a certain level. The hair follicles must also be sensitive to these signals.

As these levels rise, the fine vellus hair transforms into thicker terminal hair.

Body hair grows in a different way than the hair on your head. Every hair goes through different stages of growth and rest. The growing stage is called the anagen phase. For hair on your head, this phase lasts for many years. For body hair, the anagen phase only lasts a few months.

There is also a resting stage called the telogen phase. This stage can last from a few weeks to nearly a year. Because the growing phase is so short, body hair stays much shorter than head hair.

Different parts of the body change at different times. Pubic hair is often the first to appear during puberty. This is because those areas are very sensitive to androgens. In industrialized countries, this often starts around age 11 for females and 12 for males. Some females may even see this change as early as age 8.

Men often grow more hair on their chests and backs. Women may see changes in thickness, but usually have less hair overall.

Even though it looks simple, body hair has a very important job. It helps you feel the world around you through touch. The hair acts like a tiny sensor for your skin. When the hair moves, it pushes on nerves inside your skin. This allows you to feel vibrations or even the movement of air. It can even help you feel a tiny insect touching you.

This sense of touch extends even beyond the surface of your skin.

Human bodies are covered in different types of hair that serve various biological roles. Most people have a layer of vellus hair covering almost their entire body from childhood. This hair is very fine and light in color, making it difficult to see.

There are only a few exceptions where vellus hair does not grow, such as the palms of the hands, the soles of the feet, and the lips. During and after puberty, a different type of hair called androgenic hair, or terminal hair, begins to develop. This hair is much thicker and darker than vellus hair.

The transition from vellus to terminal hair is a key part of human development.

The growth of androgenic hair is driven by a specific biological mechanism involving hormones. It depends on the levels of androgens, which are male hormones, in the body. It also depends on the density of androgen receptors located in the dermal papillae. The dermal papillae are the structures at the base of hair follicles. For hair follicle cells to multiply, both androgen levels and receptor density must reach a certain threshold.

As these levels rise during puberty, the fine vellus hair transforms into coarser terminal hair. This process happens to varying degrees across most human populations.

Androgenic hair follows a different growth cycle than the hair on the scalp. Every hair goes through an anagen phase, which is the active growth stage. For scalp hair, this phase lasts for many years. However, for androgenic body hair, the anagen phase only lasts a few months. There is also a telogen phase, which is a dormant or resting stage. The length of the telogen phase varies by location, ranging from a few weeks to nearly a year.

This shorter growing period and longer resting period explain why body hair is much shorter than head hair.

Different regions of the body show different patterns of hair distribution. Pubic hair is often the first to appear because these areas are highly sensitive to androgens. In industrialized countries, this typically begins around age 11 for females and 12 for males. Some females may begin this growth as early as age 8.

Arm hair often concentrates on the wrists and forearms. In adolescent males, terminal arm hair growth is often much more intense than in females. Men generally develop more abundant hair on the chest, back, and limbs compared to women.

Facial hair is another major area of androgenic development. Both men and women experience facial hair growth, though the patterns differ significantly. Moustaches in young men often appear around the onset of puberty. Some men may not develop facial hair until their late teens, or perhaps not at all.

Women may develop hair around the chin, sideburn area, or upper lip. In some cases, female beard growth results from a hormonal imbalance or a rare genetic disorder called hypertrichosis.

Beyond appearance, androgenic hair serves a vital sensory function. It provides tactile sensory input by acting as a bridge between the environment and the skin. When the hair shaft moves, it transfers vibrations and movement to sensory nerves within the skin. Follicular nerves specifically detect the displacement of these hair shafts.

This allows the body to detect air movements or the contact of small objects, like an insect, before they even touch the skin. This extends the sense of touch into the space surrounding the body.

Cultural practices and history have also shaped how people interact with their body hair. For example, the practice of shaving underarm hair became popular in the United States and United Kingdom around 1915. This was largely due to advertisements in magazines. The widespread use of the safety razor at the start of the 20th century made regular shaving much easier. Today, many people shave hair on their legs or arms for cosmetic reasons or for sports. Athletes like swimmers and cyclists may shave to reduce friction or highlight muscle development.