“Beauty has no skin tone”. Unknown
Are you curious to know why people with dark skin tan more easily, or why white skin is more prone to premature skin aging?
In this blog, I will reveal all the scientific reasons in the simplest way, but first let’s understand together what skin is and what it is made up.
What is the skin?
Skin is the largest sense organ in the human body, made up of several different parts, including water, protein, fats, and different minerals and chemicals. It has three layers; epidermis, dermis, and hypodermis (1).
The epidermis is the external layer of the skin, the one we see and touch. Its main functions are to protect us from the attack of bacteria and toxins, from the loss of water necessary for optimal hydration, to produce pigments and to protect the immune system. Epidermis itself has 5 layers, the most superficial layer is called stratum corneum and the deepest one is stratum basale, where the stem cells are located. The epidermis is constantly renewed in a month and dead cells that have reached the surface require 14 days to be removed.
The dermis is the middle layer. It is thick and elastic and its functions are to protect the body from all external aggression and polluting components and to give the skin the necessary nourishment. The dermis contains: blood vessels, sebaceous glands, lymphatic vessels and sensory receptors. Its major structural components are collagen and elastin that are essential for healthy and young skin.
The hypodermis is the deepest layer of the skin, and its functions are to store energy while carrying out a task of protecting and isolating the body at the same time. It’s made up of fat cells that protect the body from heat and cold and collagen fibers that keep fat cells together and blood vessels.
Although skin structure is relatively the same among different races, there are some variations among ethnic skin types in terms of response to environmental factors and aging. Here, I have listed the major differences between white and colored skin (2).
1) Pigmentation, which is the result of genetics, exposure to the sun, or both. The actual skin color of different individuals is affected by many substances, but the single most important substance is called melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skin humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in the veins of the dermis. Melanin’s function is to protect the skin from UV radiation and to create a real barrier. The black epidermis allows only 17.5% of UVA and 7.4% of UVB to penetrate, while white skin allows 55% of UVA and 24% of UVB to absorb. Therefore, white skin is more affected by UV rays, with higher risks of rashes and sunburn making it more prone to dark spots and skin cancers. This is why people with lighter skin need to use products with higher SPFs. Furthermore, white skin has a greater predisposition to premature skin aging and the appearance of wrinkles and fine lines, while darker and more pigmented skin keeps the skin younger for longer.
2) The number and size of subcutaneous glands: Black skin has a greater gland pore size, increased scent and sweat glands and greater sebum secretion (an oily, waxy substance produced by your body’s sebaceous glands). That is why products with astringent and mattifying properties are recommended for black skin. This probably accounts for the higher microbial flora present on black skin. One study have shown increased aerobic bacteria (650% greater) and Candida albicans (150% greater) on black skin compared to white skin.
3) Skin structure: Stratum corneum layer is more compact in black skin compared to white skin even though it has the thickness in both; about twenty cell layers are observed in blacks versus sixteen layers in whites. Black skin contains low lipid levels and high protein cohesion. This structure has potentially caused a slightly inferior permeability of black skin to certain chemicals. The increased cohesivity may also explain the reduced potential to irritate black skin.
So, Skin types defined as white and colored demonstrate significant differences in the structure, organization, and sensitivity to external factors such as chemicals. This can translates further into different demands regarding preventive measures and relevant cosmetic product applications. Personalized skincare is an actively growing area with the biomedical and commercial applications that could provide new generation of skin products.
I hope I have been helpful with this article. Feel free to contact me at email@example.com if you have any questions.
Stay Amazing, Stay Beautiful
Dr. Zahra Motahari