Background
The melanocyte is the cell responsible for the production and distribution of melanin. Melanin is the pigment that determines much more than just the colour of our skin but helps to determine our race as well. High levels of melanin has many beneficial properties for overall skin health. The most significant benefit is protection from the sun's ultraviolet radiation and subsequent defence against ageing and skin cancer. Disorders of melanin however can lead to hyperpigmentation of the skin. Skin pigmentation is of great cultural and cosmetic importance. Let's delve deeper into the science behind skin pigmentation.
The melanocyte
Melanocytes are large cells that sit at the bottom of the epidermis (the top layer of skin). They have long tentacle -like projections that are used to secrete melanin into the other skin cells of the body. The more melanin secreted into our skin cells, the darker we are. The number of melanocytes does not vary from race to race. What sets us apart from one race to another is the size of the melanocytes and the intensity of the melanin that they can produce. Understanding how melanin is produced is the key to understanding disorders of pigmentations and the ways in which they can be managed.
Inside the melanocyte, the amino acid tyrosine is converted into melanin by the enzyme tyrosinase.
Too much conversion of tyrosine into melanin can lead to disorders of pigmentation. In order to improve hyperpigmentation, we must use products that target the tyrosinase enzyme.
What stimulates the production of melanin
The sun
The sun emits ultraviolet (UV) radiation. UV radiation penetrates the skin and causes cellular and DNA damage. Melanin, the body's natural sunscreen, absorbs the sunlight and scatters the ultraviolet radiation preventing it from ageing the skin or causing malignant melanoma.
There are two types of UV radiation that damage the skin:
UVA radiation produces ‘free radicals’ that damage the skin cell's structures and leads to the characteristic signs of ageing such as wrinkles, sunspots and fine lines.
UVB has the ability to penetrate through glass and burns the skin. It causes mutations to occur in the cells. UVB exposure puts the skin at risk of all three types of skin cancer (Basal cell carcinoma, squamous cell carcinoma and malignant melanoma).
The melanocytes produce melanin in response to ultraviolet light in order to protect the skin from DNA and cellular damage. The more sunlight directed onto the skin, the greater the production of melanin. This is why we tan in the sunlight and why our areas of hyperpigmentation get darker.
Inflammation
Damage to the skin leads to breaks in the skin's tissue and this causes inflammation. Inflammation stimulates the melanocytes to deposit melanin along the site of injury. Factors that lead to damage in the skin include: acne, eczema, allergic rashes, medications and cosmetic products. Anything that irritates/ causes breaks in the skin causes inflammation. Inflammation, even on a small scale can cause hyperpigmentation.
Acne is the major cause of hyperpigmentation. Where a spot damages the skin, melanin granules are deposited at the site of damage. This leads to an uneven distribution of melanin and uneven skin. Some treatments or cosmetic products aimed at reducing acne might actually exacerbate the problem. Harsh scrubs and cleansing brushes when used regularly may cause trauma and inflammation to the skin. Prolonged use of these can cause microtears to appear in the skin which eventually leads to hyperpigmentation.
Individuals with sensitive skin are most at risk of hyperpigmentation. The skin acts as a barrier to the outside world. Those with sensitive skin have breaks in this barrier, making their skin more susceptible to irritation and inflammation.
Melasma
Melasma is a chronic skin condition that causes asymmetrical, blotchy hyperpigmentation on the face, arms and back. It is a common issue for skin of colour that can lead to embarrassment and distress. Triggers for melasma include: UV radiation, pregnancy, oral contraceptives, some scented soaps and hypothyroidism.
Dark under-eyes (periorbital hyperpigmentation)
The area under the eyes is particularly prone to hyperpigmentation. This is because the skin around the eyes are some of the thinnest in the whole body. The dark circles leave us looking unwell and tired. Our genetics might make us more susceptible to some of these factors for instance having naturally thin skin around the eyes might will cause you to be more at risk of hyperpigmentation around the eyes when you're exposed to the following:
UV radiation (the sun)
Drugs
Hormones
Allergies