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Why sunscreen is the only anti-ageing product you need

The sun’s rays cause the majority of skin changes as you grow older. Here’s how sunscreen helps prevent the damage.

Have you ever looked at the skin on the buttocks of a 90-year-old? Dr Fayne Frey has. “It’s beautiful,” said the dermatologist and author of the book The Skincare Hoax. “There’s very little pigment, there’s very little wrinkling, there are very few blood vessels.”

Compare that to the skin on a nonagenarian’s face, where you’ll likely see brown spots, scaliness, visible blood vessels, much more wrinkling and a generally sallow appearance.

Some signs of ageing, namely fine lines, happen naturally over time. But Frey said that as much as 80 per cent of the skin changes we associate with age are actually caused by the sun’s ultraviolet rays. The best way to avoid them, aside from staying indoors, in the shade or permanently covered up? Sunscreen.

Sunscreen’s ability to block sunburns and prevent skin cancer is well known, but many dermatologists say it’s also the best skin care product for slowing signs of ageing. Here’s what to know about how UV rays cause the skin to age and how sunscreen helps to minimise those effects:

How UV rays damage the skin

There are two categories of ultraviolet light: A and B. UVB wavelengths are shorter and primarily affect the top layer of the skin. UVA rays are longer and can penetrate deeper (they can also travel through glass, so don’t assume a window keeps you safe from sun damage).

Years of exposure to both UVA and UVB rays damages cells on the top layer of the skin, called keratinocytes. When that happens, the skin starts to look red, rough and scaly in patches — a condition called actinic keratosis.

“It’s due to DNA mutations that occur specifically in the keratinocytes, and they then proliferate and become abnormal,” said Dr Lena Von Schuckmann, a dermatologist and clinician researcher at the University of Queensland in Australia. In some cases, actinic keratosis can become cancerous.

Below the keratinocytes are the melanocytes — the cells that produce melanin and cause the skin to darken. UVA rays primarily activate these cells, resulting in a suntan. (Sunburn is different; it’s caused by UVB rays injuring the top layer of the skin.) With long-term UV exposure, the melanocytes become damaged, resulting in permanent hyperpigmentation. These brown spots are sometimes called sunspots, age spots, liver spots or their technical name, solar lentigines.

Collagen and elastin, which keep the skin elastic and supple, reside in the next layer down. UVA rays trigger the breakdown of those proteins, causing wrinkles as the skin loses its elasticity, as well as the thinning of skin, making blood vessels more visible.

There’s no real way to boost collagen and elastin artificially (there’s scant evidence for the power of supplements and creams), but cells called fibroblasts do continue to make the proteins as you age, although production slows down. As a result, some dermatologists say it may be possible to reverse some signs of aging.

If you start using sunscreen early and consistently enough, “and the fibroblast is still young enough or healthy enough to be able to produce more collagen,” the appearance of wrinkles could diminish over time, said Dr Henry Lim, a dermatologist at Henry Ford Health and a former president of the American Academy of Dermatology. The key is making sure collagen levels aren’t depleted further by sun exposure while the cells work to replenish the protein.

But Von Schuckmann said the jury is still out: “We certainly have studies to show that sunscreen used on a daily basis reduces skin ageing. Whether or not it reverses skin aging, that’s a little bit tricky to differentiate.”

How sunscreen prevents signs of ageing

Sunscreen stops damage by blocking UV rays from reaching and penetrating the skin. There are two types of sunscreen ingredients: Mineral and chemical.

Mineral ingredients, namely zinc oxide and titanium dioxide, act as a physical barrier, reflecting the ultraviolet light off the skin. (Our eyes can detect that reflection of light, which is why these sunscreens appear to leave a white cast.) Chemical ingredients — such as avobenzone, oxybenzone and homosalate — absorb the UV rays. Both types of sunscreen can degrade or wash off over time, so it’s important to reapply every two hours, and more frequently if you’re swimming or sweating.

In general, sunscreens are more effective at stopping the shorter UVB rays than the longer UVA rays. Sun protection factor, or SPF, only refers to how well the sunscreen prevents a sunburn, meaning how well it blocks UVB.

Frey said that just a few ingredients approved for use in the United States — namely avobenzone, oxybenzone, zinc oxide and, to a lesser degree, titanium dioxide — block UVA. To make sure a sunscreen provides UVA protection, look for one with these ingredients, or check that it’s labeled “broad spectrum,” which means that it stops the longer wavelengths from penetrating. (Newer ingredients available in Europe are more effective against UVA; some are in the pipeline for review by the Food and Drug Administration.)

When it comes to choosing the best sunscreen to prevent signs of aging, Von Schuckmann advised looking for one that’s broad spectrum and SPF 50 or higher; whether it’s a chemical or mineral formulation doesn’t matter. The most important thing, she added, is that it “actually goes onto the skin every single morning.”

This article originally appeared in The New York Times.