7 concepts about hair, so you understand everything!

Have you ever wondered, What is hair? Why does hair grow and fall out? Why does it have color? We will review the most interesting topics in the basic science of hair, so that you too can be (almost) an expert.

1. What is hair?

This is an important question to understand the rest. Hair itself is a structure composed of dead cells filled to the brim with keratin, which gives it strength and is what is visible outside the skin. Each hair on the body (which is practically on all surfaces except palms and soles) is generated by a group of cells called the hair follicle. The hair follicle is often understood as the root of the hair because it is the structure that generates it throughout life. Each root can generate many hairs throughout life, as it does not fall out with the hair, but rather stays within the scalp. So when you see a hair fall out, don't think it has fallen out with the root, as many people tell me when they see a white dot. If that happened, we would all be half bald!!!! The roots are firmly anchored 4mm deep in the scalp and are only destroyed by some diseases.

2. Do you know the structure of hair?

Hair is not a single elongated structure, but rather is made up of many cells that join together like a wall. In thick hairs, these cells are distributed in 3 layers. A medulla in the deepest part that gives it strength (like a spinal column). This is followed by the layer called the cortex. It is the most important because it contains the hair's color and also, depending on how it forms, it will give the hair its shape. That's why there are curly hairs and straight hairs. Finally, they are covered by an outer layer called the cuticle. It is very interesting because it has a structure like a roof with its tiles, and just like a roof, its function is to prevent unwanted substances from penetrating and damaging the fiber. That's why it is always said that it is so important to keep the cuticle healthy if we want the hair to look good.

3. Are all hairs the same?

NO! Dermatologically, there are considered to be 3 types of hair, although in adults generally only two are seen. Depending on the person, hair will change color or shape, but the basic structure is always the same as we mentioned. In adults, we see two types of hair: the thicker hair found on the head, genitals, or armpits, which is called terminal hair, and the hair on the arms, legs, chest, or face, which is called vellus hair. The third type of hair is what fetuses have, and some are born with it. This type of hair is called lanugo and is the finest hair that exists, but it falls out in the first months after birth.

4. How does hair grow?

Hair is formed by the cells in the hair follicle, and for this, they multiply, forming a kind of brick tower. This tower fills up from below, but the more it grows, the thicker it gets. BUT! (everything has a but!) it will not grow forever until we die. The cells of the hair follicle can stop building this brick tower at any time and cause it to fall out, and then form another. This is called hair growth cycles. The duration of the growth phase is genetically determined, which is why some people can have very long hair and others not so much. But it is also related to external causes that can prevent hair from growing, such as a very strict diet.

5. And why does my hair fall out?

There are millions of reasons why hair can fall out naturally. The first is that it was simply time for it to, which is why we shed approximately 100-200 hairs daily, and this is natural. Sometimes more hair than usual falls out; generally, this happens when the hair follicle and all its cells try to protect themselves from being destroyed. The hair follicle is one of the most active structures in the body, along with the bone marrow (responsible for generating blood cells). Being so active, they can be easily damaged if not protected, and their way of protecting themselves is to stop working. Therefore, when this happens, hair falls out, but soon after, another begins to grow. Only in cases of illness may healthy hair not grow, which is why if there is excessive or prolonged hair loss, dermatological evaluation is recommended.

6. Why can hair have different colors?

Each person has hair of a different color, and in fact, with age, gray hairs appear, which is the loss of hair color. What makes hair have color and establishes that color is melanin, just as it happens in the skin. Among the cells that form the hair follicle, at the base of that brick tower we mentioned, are the cells responsible for giving color, which are melanocytes. These can form pheomelanin (which is for blonde or reddish hair) or eumelanin, which gives brown or black hair its color. Hair tones will then vary depending on the quantities of melanin that are formed. In general, the more eumelanin, the darker the hair will be, and the more pheomelanin, the lighter. Gray hairs will appear when these melanocytes begin to function less effectively and stop producing color.

7. Why does hair change throughout life?

It's very easy to observe how hair changes throughout life. As children, our hair is generally finer, softer, and has less color. When we reach adolescence, hair in certain areas of the body becomes thicker, mainly in the armpits, genital area, and on the face. And finally, when we reach a certain age, this hair gradually loses quality in a more or less noticeable way. All these changes occur because the hair follicle responds to the instructions given by hormones. Depending on the stage of life, but also on each person's genetics, these hormones make hair grow better or worse. When these instructions do not work completely correctly, conditions such as androgenetic alopecia or hirsutism can appear.