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Sunday, July 6th, 2014

Science Confirms ‘Black Don’t Crack’: More Pigment Delays Some Effects of Aging

When I remarked to a friend of mine that she never seems to look any older as the years go by, she replied: “That’s because black don’t crack”. Not the answer I was expecting, but after she convinced me that this is a common term, I looked into the evidence, and discovered that she is at least partly right.

There are two factors that cause skin to age: chronological ageing and photoageing. None of us can avoid chronological ageing – like it or not, we cannot stop the passing years from leaving their mark.

But photoageing is a different matter. It does vary according to your skin colour, a result of the varying degrees of pigment that we produce.

The darker your skin, the larger the pockets in skin cells known as melanosomes, and these contain the sticky pigment melanin.  Very pale skin produces almost no melanin, while Asian skins produce a yellowish type of melanin called phaeomelanin, and black skins produce the darkest, thickest melanin of all – known as eumelanin.

It’s not just the size of these pockets in skin cells that differs, but also the density of melanin packed within them. In black skin the melanin is packed so tightly that it absorbs and scatters more light, giving you more protection from the sun’s ultraviolet rays.

Surprisingly few studies have been conducted on this topic in recent years. But if you go back to 1979 there was  a study from Kays Kaidbey and his colleagues in the United States, which found that on average 55% of ultraviolet A rays penetrate Caucasian skin while fewer than 18% get through African-American skin. This is why photoageing is delayed in people with dark skin.

The Fitzpatrick Scale was devised in 1975 to classify the response of different skin types to ultraviolet light. It divides skin into six tones; from people of type I who have red hair and very fair skin which burns easily, through to type VI black skin, which rarely burns and can tan, but only a little.

The greater quantities of melanin give people with black skin some protection against both wrinkles and skin cancer. But that does not prevent you from getting skin cancer completely. Reggae legend Bob Marley famously died from the cancer, which eventually spread from a malignant melanoma on his big toe.

In people with skin types IV (Asian skin) through to VI, photoageing is delayed and many people notice very few lines on their faces before they reach their fifties or sixties. (Still, there is individual variation, and a minority will look in the mirror and see those tell-tale lines appearing at a younger age.)

However, it is not quite true to say that black skin never wrinkles. Photoageing does occur eventually and is faster in African Americans than in those of African or Afro-Caribbean descent.

But although photoageing is delayed, other signs of ageing skin are not. Black skin is more prone to age spots, to dark patches on the skin and to harmless brown growths known as seborrheic keratosis.

To read the entire story Claudia Hammond, BBC

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