Why does the sun darken the skin? The answer is due to melanin.
To better understand, we need to go deep into the membranes of the skin. Skin cells and components such as hair follicles, sweat glands and sebaceous glands form the skin’s first line of defense against external influences.
Skin is made up of 3 layers: the epidermis, the dermis, and the dermis . Each layer has a distinct cellular structure with different functions.
Dark skin is caused by melanin.
To understand why skin darkens when exposed to a lot of sunlight, we need to focus on the outermost layer of the skin: the epidermis.
The epidermis consists of two main cell types: keratinocytes and melanocytes.
Keratinocytes form the skin’s surface base and are the first layer to be affected by the environment. At the bottom of the normal layer are melanocytes. These astrocytes are responsible for the production of melanin, which protects the skin against ultraviolet (UV) rays from the sun.
How is Melanin Made?
Inside each melanocyte there are many specialized pigment cells called melanosomes . The chemical reactions occurring inside the melanosomes turn the amino acid tyrosine into melanin.
When sunlight hits the skin, UV rays can penetrate the body causing DNA damage and can cause skin cancer. At that time, the melanocytes will increase the production of melanin and transport them to the keratinocytes. Melanin will cover the cell nucleus, forming a protective “shield”. They absorb ultraviolet rays and prevent them from attacking the DNA inside the cell nucleus.
Therefore, the more the skin is exposed to the sun, the more melanin the body produces and the darker the skin becomes.
Besides melanin, genetic factors also contribute to the degree of tan of each person.