Despite being an important part of our body, hair is not well known by the general public. And it is particularly distressing when one starts losing hair heavily. Here, we will try to give a “vue d’ensemble” and provide a few key points on hair:


1. Hair on our scalp

Let’s start by stating that our hairs follow a specific cycle and renew themselves throughout our life. The visible part is actually biologically dead: our hairs grow thanks to the only part of them that is alive i.e. the root embedded in the scalp also known as hair follicles.

We, usually, have on our scalp between 120,000 and 150,000 hairs each with a diameter ranging between 50 and 100 micrometers. However, different factors such as ageing, health conditions, or genetics can lead to loss of hair.


2. Hair is made up of two parts

  • The root or hair bulb, the living part of the hair, is embedded in a hair follicle. This is where the keratinocytes that compose the hair are produced, along with the melanin that colors it.


  • The shaft is the visible part of the hair, but it is biologically dead: it is made up of dead keratin-filled cells. You might have read some articles about “how to revive dead hair?” but this is not true. Simply put you can’t revive dead hair because it is just a dead fiber.

3. The Shaft is structured in 3 layers

Indeed and those 3 layers are called Cuticle, Cortex, and Medulla:

The cuticle, the outmost layer of the hair responsible for hair shine and smoothness. It is made up of keratin scales and takes shape of tiles on a roof. Hairs are covered in an oily layer of sebum produced by the sebaceous gland embedded in each hair follicle. This substance is essential to their good health. It protects them, nourishes them, and keeps them soft and shiny. Most hair products such as shampoos and conditioners interact with this layer;

The cortex, the inner structure of the hair which is responsible for fiber flexibility and strength. The cortex envelops the medulla and is composed of two types of keratin fibers – horizontal and vertical – that make the hair supple and strong. Moreover, the cortex contains the melanin pigments that give hair its colouration.

The medulla, a soft substance located at the inner core of the hair fiber. It is composed of agglomerated cells with no nucleus. We do not yet fully understand its role;

4. Hair is composed of mostly keratin

Hair is protein and made up of mostly amino acids. It is composed of more than 80% Keratin, 10% water and 5 to 10% pigments and lipids. Keratin is a structural hard and fibrous protein found in our hair, skin, and nails.

Keratin is synthesized by keratinocytes and is insoluble in water, thus ensuring impermeability and protection for the hair. The structure of hair is what makes it have different properties than skin and nails.

5. Hair color comes from melanin

Hair colour is the result of  melanin, a natural pigment produced by cells called melanocytes, located in the root. There are cells in the follicle that create melanin pigments which are injected into the growing hair fiber. These melanin pigments are responsible for all the natural hair colors observed. There are two different types of melanin: the first (eumelanin, brown to red) is responsible for brown, dark and black hair, whereas the second (phaeomelanin, red to yellow) colours blond and red hair.

The colour is more or less intense, depending on the amount of melanin present in the hair. Each individual’s hair colour is encoded in their DNA, though external factors such as sun exposure can contribute to lightening it. During the ageing process, melanocytes decrease and become less abundant. Consequently, this is when we start to get grey or white hairs meaning that they are almost devoid of melanin.

6. Gray hair is the absence of melanin

Gray or white hair is what results when no melanin is injected into the fiber. Those are just “uncolored” hairs.

7. The shape of a hair fiber depends on the shape of its follicle

Hair gets pushed out of the head through a tiny hole. The more circular the hole, the straighter the fiber. The more elliptical the hole, the curlier the hair.

8. There are 3 stages of hair growth

The cycle of renewal goes throughout our life, our hair grows, falls out, and grows again. Our hair follicle is capable of producing around 15 successive hairs before its activity stops and it dies.

Hair growth happens in three successive stages. They are called Anagen, Catagen & Telogen:

  • The anagen stage, which lasts from 2 to 7 years, during which hair strands get longer. Hairs grow at about 1 cm per month. New keratinocytes are produced in the hair bulb and push the oldest ones out, thus lengthening the hair;
  • The catagen stage, which lasts 2 to 4 weeks, is a transition time when the hair fiber stops growing and detaches from the growth portion of the follicle.
  • The telogen stage, which lasts 1 to 4 months, is a dormant phase of the hair follicle. The hair is shed naturally and happens before a new cycle begins. At the end of this phase, a new anagen phase commences. In this cycle process, our hair density remains visible (except in cases of alopecia or other conditions).


9. Hair fiber diameter changes as people age

Hair fiber diameters start out thin and get thicker as an individual enters adulthood. Through ageing, it begins to get thinner and hair length changes as well with older adults having usually shorter growing hair.


10. The isoelectric point of a hair is near pH 3.67 while its isoionic point is around pH 5.6.

This means that any product applied to hair that has a pH higher than 3.67 increases the static electricity and the repulsion between strands. Moreover, Alkaline pH may increase the negative electrical charge of the hair fiber surface and, henceforth, increase friction between the fibers. In addition, this may lead to cuticle damage and fiber breakage. It is a fact that the lower pH of shampoos may cause less frizzing for generating less negative static electricity on the fiber surface.


Our hair can change with the changes in our body. Ageing, hormones, diet & lifestyle, stress, Vitamin deficiencies are a few factors of these changes. Most people at some point in their lives have experience hair loss. If you are suffering from hair loss, do not hesitate to book a consultancy at Nar London, Harley Street (£50 that can be redeemed against the treatment).


Remember the earlier you take an action, the quicker and better results you would get. Treatment like PRP can potentially help.