• Núria Estapé, science journalist

    The colours of our skin

    The human species has three broad ethnic types: black, Asian and Caucasian. This division, if not scientifically accurate, is convenient. Skin colour reveals, almost always at a glance, what ethnic type we belong to. But the difference in skins is not just a matter of pigmentation. The characteristics of the stratum corneum, glands and microflora also affect how skins age and what risks they face.

     

    When comparing the appearance of black, white and Asian people, we often refer to skin colour. Ethnic differences are showcased by the body’s largest organ, the skin. But is colour the only difference between skins? Do different skins age differently? Which skins are more sensitive to chemical and environmental damage?

     

    Chromophores colour our skin

    The chromophores contained in different proportions in the skin are genetically determined by ethnic origins and are responsible for the full range of human skin colour, from the most translucid white to the opaquest black. Haemoglobin and oxyhaemoglobin (present in the blood) are the pink ‘crayons’ responsible for white skin; carotenoids (also found in tomatoes and carrots) enhance the yellowish tones of Asian skins; and melanin accounts for brown and black skins. However, we all have – to a greater or lesser degree – melanin, a pigment that darkens all skins exposed to the sun’s ultraviolet rays.

     

    Dark skin ages slower

    Melanin is responsible for dark skins taking longer to show the effects of age than white skin. Dark-skinned people produce more melanin and continue to manufacture it as they age. Melanin production by other skins, however, decreases with age and with sun exposure.

    Skins age differently depending on their colour. White skins shrivel and become flaccid sooner than dark skins, whereas dark skins suffer the effects of excessive pigmentation, such as scarring after inflammation (keloids) or the appearance of irregular coloured patches.

     

    Hydration and protection

    The stratum corneum (the outermost layer of the skin) in Asian people loses less water and contains more ceramides (the fats that contribute most to skin hydration) than black skin. This keeps Asian skin hydrated even though it is usually affected by exposure to the sun, because, like white skin, it is weakly pigmented.

    Although its thickness does not vary according to skin colour, the stratum corneum of black people contains more layers of corneal cells. For this reason, the protective mantle is more compact and robust, despite the fact that it contains fewer ceramides.

    The pores, sweat glands (which release sweat) and sebaceous glands (which secrete fat) in black skins are larger. Dark-skinned people therefore produce more sebum around the hair follicles, have more microbial flora and have a lower pH (more acidic) skin.

    Because of these features, black skin is more prone to scarring from acne and to spontaneous peeling. However, it is also less sensitive to certain chemicals that irritate the skin of white and Asian people. Specifically, Asian skins, with a less compact protective barrier, seem to be the most sensitive to the effect of chemicals.

    Humans tend to live far from their homelands and to mingle with each other. Their skins and genetic characteristics are also mixed, creating thousands of combinations. What kind of skin have you got? Think about it and decide the most suitable care for it.

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