Skin Whitening Sunscreen & Sunblock: How To Avoid Or Reverse Darkening

By | January 27, 2022

Exposure to the sun causes skin to darken. This is because of the production of the melanin, a pigment that protects the lower layers of the skin from sun damage. Damaged skin produces more melanin leading to further skin darkening. Staying out of the sun or blocking sun exposure can reverse this and lighten skin back to its natural color.Structure of the skin

The skin forms the largest organ of the body. It performs many important functions including protecting the body from trauma, regulating body temperature, maintaining electrolyte and water balance, sensing pleasant and painful stimuli and synthesizing Vitamin D.

The skin consists of three layers: Epidermis, dermis and the subcutaneous layer (fat layer). Each layer has its own specific tasks to perform.Epidermis

This is the tough, relatively thin external layer of skin. The majority of cells present in the epidermis are the keratinocytes, which originate from the cells of the basal layer (deepest layer of the epidermis). New keratinocytes migrate slowly upwards towards the surface of the skin. They are shed gradually, replaced by new cells from below.

Melanocytes are the cells that are present in the basal layer of the epidermis. They produce melanin pigment, which is the major contributor to skin’s colour. However, the primary function of melanin is to filter ultraviolet (UV) radiation from sunlight. UV radiation can damage DNA and which can result in many harmful effects such as skin cancer.Dermis

The next layer of skin is the dermis. It is a thick layer made of elastic and fibrous tissue, giving the skin its strength and flexibility. The nerve endings, sebaceous glands, sweat glands, blood vessels, and hair follicles are present in the dermis.Fat/ Subcutaneous layer

A fat layer is present beneath the dermis, and it helps in insulating the body from cold and heat. It also provides protective padding and serves as an area to store energy. Fat cells are the fat present in cells. Fibrous tissue holds these cells together.What determines skin colour?

Human skin comes in various colours ranging from shades of almost white to dark brown. Melanin, among other factors, influences an individual’s skin colour. It also determines the colour of a person’s eyes and hair.Intrinsic factors

Genetics determine the levels of melanin. People whose parents are fair will inherit their parents’ fair skin, and people whose parents are dark will similarly inherit their parents’ dark skin. Constitutive pigmentation refers to the level of skin pigmentation inherited at birth.

There are also numerous other factors determined at the time of birth that influences the skin colour, such as the way the body makes hormones and the way these hormones convey information to melanin-producing cells. These genetic factors cannot be altered, and are also known as intrinsic factors.Extrinsic factors

There are certain extrinsic factors that exist outside the body which may influence the colour of the skin and impart acquired pigmentation. One of the most significant extrinsic factors is exposure to the sun’s UV radiation. The sun produces UVB and UVA rays. Different kinds of UV sun rays cause different effects on skin colour.

Exposure to UVA rays influences the melanin present in the upper layers of the skin. This causes immediate pigmentation. Skin pigmentation that occurs a few days after exposure to the sun is due to the production of new melanin in response to exposure to UVB rays. Other extrinsic factors that influence the colour of skin include damage to DNA and age. The way the body produces melanin changes as an individual age.Melanin

Melanin is a skin pigment present in skin cells. There exist two kinds of melanin that produce visibly different effects on skin pigmentation.Pheomelanin, a yellow-red coloured melanin, is the primary melanin present in people who have fair skin.Eumelanin produces pigmentation of a dark brown colour and it is the primary type of melanin present in people who have dark skin. Eumelanin provides better protection from the sun’s UV rays in comparison to pheomelanin. Hence, fair-skinned persons are at higher risk of getting sunburn.

Genes determine the content of melanin present in the skin. This implies that a person inherits their skin colour from their parents. Specifically, a gene referred to as SLC24A5 has been identified as a major determinant of skin colour.

The more melanin made by a person’s skin, the darker their skin will be. Some individuals make more melanin than others. Every individual has approximately the same number of melanin-producing cells but everybody does not make the same quantity of melanin.

The total amount of time spent outdoors and exposed to the sun also influences melanin levels, as the body increases its production of melanin upon sun exposure. A person who works outdoors every day in the sun develops more tanned or darkly pigmented skin over time in comparison to if they would have worked indoors every day.

Why some people have more melanin than others

Melanin has a key role to play in protecting the body from UV rays as it helps to filter the sun’s rays before they can cause damage to skin cells. Sun exposure stimulates the body to make more melanin to protect the skin cells.

A person’s skin colour is closely associated with what part of the world they come from. People who have dark skin originate from places which have higher levels of UV radiation or places that are closer to the equator.

Melanin is produced in special cells referred to as melanocytes. Melanogenesis is the process by which melanocytes make the pigment melanin. They are abundantly present in the basal layer of the epidermis and also the underlying dermis.

DNA is damaged upon exposure to UV rays. This triggers growth factors, cytokines and other types of inflammatory factors. It also stimulates melanin synthesis. Granules of melanin produced in melanocytes are transferred to the cells called keratinocytes. Both these cells form a protective layer in the inner epidermis, absorbing UV rays and inhibiting their penetration.

Melanin synthesis starts in the liver, where phenylalanine converts to tyrosine. The enzyme phenylalanine hydroxylase catalyzes this reaction. Melanosomes,  which are cell organelles present in melanocyte, produce melanin. L-Tyrosine is oxidized to form L-DOPA and the reaction is catalyzed by the tyrosinase enzyme. Other enzymes which are involved in melanin synthesis are TRP1 (tyrosinase-related protein 1) and TRP2 (tyrosinase-related protein dua). L-DOPA is then oxidized to form DOPAquinone. From here, the pathway to synthesize melanin diverges to produce either pheomelanin or eumelanin. Melanosomes get transferred to the keratinocytes.

Melanin is stored longer in people with dark skin but degrades quickly in people with light skin.

For the determination of skin colour, the type of melanin pigment produced by cells is more important than the number of melanocytes. The quantity and size of melanosomes also help in determining the colour of the skin. Darkly pigmented skin is associated with more prolific, elongated and larger melanosomes.Factors that add pigmentation to the skin

If the body’s melanocytes produce an excessive amount of melanin, this can cause hyperpigmentation. Some factors that increase melanin production include:

The major cause of the skin darkening is sun exposure as sunlight triggers the production of melanin. Melanin acts as the skin’s own natural sunscreen as it protects it from the sun’s harmful UV rays, resulting in tanned skin. However, excessive sun exposure can result in a disruption of this process and can lead to hyperpigmentation or dark skin. Moreover, once dark spots have developed, exposure to the sun may aggravate them by making melasma, age spots, post-inflammatory hyperpigmentation or even darker freckles.

Hormonal changes can cause a specific type of hyperpigmentation, called chloasma or melasma. Commonly present among females, the female hormones progesterone and estrogen on sun exposure cause the stimulation of melanin production. Melasma is also referred to as “the mask of pregnancy” as it primarily affects pregnant females on the face.

Age is a factor in darkening of the skin. As a person get older, their skin’s ability to repair itself is reduced; hence, the damage across many years becomes visible. Exposure to UV rays is one of the most common causes of dark skin.

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