Understanding Skin Pigmentation – Part One

Causes and Influences

Skin pigmentation, which determines the colour of our skin, is primarily influenced by the amount of melanin our bodies produce. Melanin is produced by cells called melanocytes in the top layer of the skin, the epidermis. There are two main types of melanin: Eumelanin and Pheomelanin. The balance between these two determines an individual’s skin tone, with eumelanin resulting in a darker skin tone and pheomelanin leading to lighter tone.

Eumelanin

Eumelanin is a dark brown pigment that provides several protective benefits. It is more abundant in people with darker skin tones and offers significant protection against harmful ultraviolet (UV) rays from the sun. Because eumelanin absorbs UV rays effectively, it helps prevent sunburn and reduces the risk of skin cancer. In addition to protecting the skin, eumelanin also plays a role in regulating body temperature by absorbing solar heat, keeping the body cool in hot conditions

Pheomelanin: The Lighter Pigment

Pheomelanin has a yellow-red tint and is found in higher amounts in individuals with lighter skin tones. Unlike eumelanin, pheomelanin is less effective at absorbing UV rays, which makes those with lighter skin more susceptible to sunburn and sun damage. However, pheomelanin also has its advantages. It helps to reflect heat, which can assist in keeping the body cool in warm environments.

The Role of Genetics in Skin Pigmentation

Genetics play a crucial role in determining skin colour. Our genes influence how much eumelanin or pheomelanin is produced, affecting not only skin tone but also hair colour and sensitivity to sun exposure.

Genes also regulate the production and distribution of melanin, and they can vary widely between individuals and ethnic groups. The number of melanocytes (the cells that produce melanin) and how active they are in producing melanin are both determined by genetics. For instance, people with darker skin have more active melanocytes that produce higher levels of melanin compared to those with lighter skin.

Sun Exposure and Its Effects on Skin Pigmentation

Sun exposure is one of the most common causes of changes in skin pigmentation. When the skin is exposed to the sun, it produces more melanin as a defence mechanism against UV rays. This increase in melanin leads to a darker skin tone, commonly referred to as a tan.

The process of pigmentation due to sun exposure involves several stages:

1. UV rays generate free radicals, which can damage skin cells.

2. These free radicals, along with UV light, stimulate melanocytes to produce more pigment.

3. The enzyme tyrosinase converts the amino acid tyrosine into melanin, which can appear red or brown.

4. Tyrosinase activity increases, leading to more pigment production.

5. Over time, as skin cells naturally exfoliate, melanin is shed, but some remains, giving the skin its colour.

NEXT – Part Two. When pigmentation goes wrong