As crass racial stereotypes go, the old adage “black don’t crack” – i.e. that black skin doesn’t wrinkle with age – is right up there. But it’s not far from physiological fact. According to the experts, skin colour does affect how the skin ages, and broadly speaking, the darker the skin, the longer it will take to show lines and wrinkles. For one, black and Asian skins tend to have a thicker dermis layer compared to white skin, founder of non-surgical treatment company Naturaskin, Dr Jasmeet Baxi explains: "By being thicker it contains more collagen. By having more collagen in the skin, in effect it can delay the visible signs of ageing." Dr Askari Townshend, who runs Askinology clinic in London, explains the main reason that the signs of ageing appear "so, so much later" in people with darker skin tones is because of their natural protection from sun damage. "Because we have different amounts of melanin in our skin, that offers us different amounts of natural sun protection and that in turn changes the way that UV radiation damages us. There actually is truth to that whole thing about black don’t crack because that person is walking around with a natural SPF for their entire lives," he says. Quick science lesson: everyone has melanin in their skin; it’s the pigment that gives our skin colour. There are different types, the two main kinds being eumelanin and pheomelanin. Eumelanin is the pigment that makes our skin darker, and it’s also the one that protects our skin from UV radiation, while pheomelanin gives the skin its red or pink shades. Lots of eumelanin means a darker skin tone, whereas if you’re fair or a redhead, you’ll have some pheomelanin in there as well. "Black skin generally has a much slower rate of photo-ageing, because the eumelanin is more effective in protecting against UV damage,” explains Dr Stefanie Williams, a leading dermatologist and founder of European Dermatology London clinic. People with black skin can start to show the signs that we usually associate with ageing – i.e. lines and wrinkles – as much as 20 years later than people with white skin tend to. Dr Baxi puts it another way: "The SPF of very dark skin may be naturally as high as 13.4, compared to three or four, or even less for Caucasian skin." One thing the doctors make clear is that when it comes to skin ageing, it’s not so much your racial heritage that plays a part; it’s literally the colour of your skin. Or to put it in doctor speak, it’s where you fall on the Fitzpatrick Scale – that’s the official scale used to categorise skin colour, ranging from Skin Type 1 (Jessica Chastain) to Skin Type 6 (Lupita Nyong’o). "If you take two siblings with the same parents, one parent might be black and the other parent white, the children can have completely different skin tones, and will age at different rates," explains Dr Williams. Of course, lines and wrinkles aren’t the only signs that skin is starting to deteriorate. Problems with hyperpgimentation and uneven tone are another indicator that the years are catching up with your skin, and the doctors say that it’s this type of problem that people with darker skin tones are likely to see. "The people with the skin types 3 and 4 particularly are more prone to pigmentation disorders," explains Dr Townshend. "For example, I’m a skin type 5, and I’m prone to post inflammatory hyper pigmentation (PIH). If I cut myself shaving or I get a pimple, I get a brown mark, and that brown mark hangs around for a long time. Whereas if I was white it would be much less likely that I would get that brown mark. I would get a pink mark and that would probably just pass." Very dark skins get pigmentation problems too, but Dr Townshend says that often they go unnoticed purely because it’s harder to see the discolouration. "People think that black skin is very resilient, it’s not," says Antonia Burrell, a London-based facialist and skincare expert. "It’s actually quite sensitive and scars easily." According to Dr Baxi, darker skin groups tend to dehydrate more quickly as they are more permeable to water. "They can often look like they do have lines," says Burrell, "but often it’s not actually lines, it’s chronic dehydration. But if they don’t address that then it will age their skin." Dr Townshend is sceptical about these findings, and points out that it can be dangerous to characterise skin too broadly based just on its colour. And of course, your melanin isn’t the only thing that determines how your skin will look as you get older. There are plenty of lifestyle factors like pollution, bad diet, stress and smoking that are no friends to your dermal tissue, and genetics plays a part too. So with all this considered, what should you be doing to take care of your skin, depending on its colour? Well, if you’re white, you should be wearing an SPF. A good one, every day. That’s not to say that you don’t need to use an SPF if you have darker skin. "Black ladies will still get pigmentation problems, and the way they can avoid them is by wearing good sun protection," says Dr Townshend. But he says, his patients with darker skin will not get the same telling off for scrimping on their suncare as the patients with fair skin will. Burrell also says it’s particularly important for patients with darker skin to keep it well hydrated, and when it comes to treating hyperpigmentation, Dr Williams says arbutin, kojic acidd and azaeic acid are the hard hitting ingredients you need to be looking out for. Of course, nothing truly stops you ageing. Black will "crack". No matter how great your genes, how well you look after skin, or what colour your skin is, no one is yet immune from the gradual deterioration of skin tissue over the years.