“Sunlight, in total, is damaging,” says Sean Christensen, MD, PhD, an assistant professor of dermatology at Yale University who researches the molecular mechanisms of skin cancer development. But, while avoiding sunlight altogether isn’t a great idea, neither is exposing unprotected skin. Once you learn how UV rays really impact your skin, you’ll be much more motivated to slather on the sunscreen. Here’s what happens below the surface of your skin — and how you can stay safe.
All UV rays are invisible, but there are different types that injure skin in various ways. The two we’re affected by are UVA and UVB (UVC rays don’t make it through the Earth’s atmosphere). “The difference between UVA and UVB rays is the depth they penetrate,” says Jennifer Linder, MD, a Mohs Skin Cancer Surgeon and the chief scientific officer for PCA Skin. UVA rays, also known as aging rays, have a longer wavelength and travel further, Dr. Linder says. Because they reach a deeper skin layer, called the dermis, UVA rays weaken the skin's support structure, causing wrinkles and sagging while also playing a role in cancer formation.
UVB rays, which cause sunburn, have a shorter wavelength and induce damage closer to the surface, Dr. Linder explains. Their high energy levels directly interact with DNA, causing damage to the epidermis, or the upper layer. But, you don’t have to burn to have fried your skin; a tan also indicates you’ve cooked some cells. “Most individuals are exposed to large amounts of UVA throughout life,” says Clara Curiel, MD, associate professor of dermatology at the University of Arizona Cancer Center in Tucson. That’s because UVA rays make up 95% of the UV radiation that reaches the Earth. What makes them so dangerous, Dr. Curiel explains, is that they penetrate clouds and glass — and no matter the season, UVA rays are present with about the same intensity during all daylight hours.
It’s the 5% of UVB rays that do significant harm to your skin, Dr. Christensen warns. That direct injury to DNA in skin cells leads to the mutations that cause surface damage as well as cancer cells. But, that doesn’t mean UVA rays are harmless; their effects just take longer to surface.
While an energy boost might be good for your workout, the added energy from UV rays causes cell meltdown. When UV rays hit the cell, helpful oxygen molecules produce free radicals that can damage cell function. “The free radicals attack cellular DNA and cause it to break apart or change structure, which could eventually lead...to cancer,” Dr. Christensen says.
“We know that over 85% of visible aging and skin breakdown is caused by external factors, particularly UV exposure,” Dr. Linder adds, "[which] increases the breakdown of collagen and elastin, leading to wrinkles and sagging.” Those cute freckles on your nose? They’re actually a form of UV damage. “Sun exposure triggers the deposit of pigment,” Dr. Linder says. “Skin cells create melanin granules as an umbrella-like protection...in an attempt to protect [cell] DNA.” The problem is that umbrella still doesn’t block 100% of UV rays, so your skin remains vulnerable.
Depending on how damaged cells react, sun exposure puts you at risk for several types of skin cancer. The most common (and least deadly) types are basal and squamous carcinoma. These cancers target the keratinocyte cells that make up the outer layer of the skin, Dr. Christensen says. After years of repeated UV damage, the DNA-mutated cells replace healthy cells and become a cancer. Once enough cancer cells are present, the healthy skin in the area can no longer do its job — and the cancer takes over.
The good news is that this cancer spreads very slowly and tends to develop in areas the sun hits, so with some vigilance you can spot basal and squamous cancers before they become dangerous. Though these cancers rarely spread, make sure to catch them early to avoid scarring and other potential complications, Dr. Linder says.
Melanoma, however, is far more serious. Melanocytes can go haywire following UV exposure — possibly even after just one blistering burn. This form of cancer grows much more quickly and is more likely to spread, which makes it so dangerous. “Melanoma is very rapidly dividing, resulting in a huge number of mutations,” says Holbrook Kohrt, MD, PhD, and assistant professor of oncology at Stanford University Medical Center who has been researching treatments that use the body’s immune system to treat melanoma. “It’s very good at escaping the immune system.”
While the majority of melanoma surfaces on the chest, arms, and legs, there are some cancers that show up in the eyes (which are very difficult to treat), on the palms of your hands, and under your nails, Dr. Kohrt says.
The most obvious evidence that you’ve let UV rays abuse your skin is seeing red — or tan. The swelling and pain from sunburn is an inflammatory response from sun-damaged cells. And, a tan is your body’s way of shielding itself from more UV rays.
“According to the Skin Cancer Foundation, just one blistering sunburn during childhood can double the chances for developing melanoma later in life,” Dr. Linder says. “The risk of melanoma also doubles if one has had five or more sunburns, no matter the age.” Age spots or uneven pigmentation also serve as red (or brown) flags that your cells are reacting to UV damage. But, they're "not an effective defense mechanism, because the pigment can’t block the damage from progressing,” Dr. Christensen says.
There's a link between “dysplastic nevi” (a term for unusual, but benign moles) and melanoma, says Steven Wang, director of dermatologic surgery and dermatology at Memorial Sloan Kettering Cancer Medical Center in Basking Ridge, New Jersey. “The sun increases the number of nevi, so their presence shows you have had a lot of sun exposure and indicates...risk of skin cancer.”
And, there is a general category of skin growths called actinic keratosis that indicate sun damage. These rough spots can look scaly, feel rough, are usually raised from the skin, and resemble warts. Often, these growths will develop into squamous cell carcinoma, so it’s good to have your dermatologist take a look if you notice any.
No need to go live in a cave; you can still repair some of your past skin sins and prevent future assaults. The first step? Ditch the idea that the majority of your sun damage happened before you turned 18. “That’s a commonly misquoted idea,” Dr. Wang says. “When you look at sun damage, the results are cumulative, so you haven’t done it all at once, [nor do you] have no hope of stopping it.” In other words, the UV rays you subject your skin to now are just as dangerous as the ones you soaked up years ago.
The most non-negotiable step is to wear broad-spectrum sunscreen, which blocks both UVA and UVB rays. And, yes, you do need to apply a layer whenever you’re spending time outside. Adding an SPF product to your daily routine will go a long way towards preventing age spots and wrinkles. “The body has mechanisms to repair DNA damage,” Dr. Wang says. “Your cells create enzymes that detect where damage is and then lay down new DNA." So, if you avoid future damage, you’re allowing those enzymes to work more effectively.
Dr. Wang is also a huge proponent of wearing clothing as a form of sun protection. Tight-knit fabrics provide a shield, and Mott 50, Athleta and Uniqlo offer lightweight styles that don’t make you look like you’re hiding under a tent. Sunglasses are also important, Dr. Wang says; your eyes are very sensitive to UV rays, and too much exposure can lead to cataracts and melanoma.
Add antioxidant-rich foods to your routine to help bolster healthy skin function: “Antioxidants are facilitators to help the body neutralize free radicals and offer a good, preventative mechanism against UV damage,” Dr. Wang says. “Vitamin C, vitamin E, ferulic acid, and green tea all offer good antioxidant benefits,” he explains. Vitamin C in the form of L-ascorbic acid has also been proven to stimulate collagen production — so you’ll be less likely to develop sagging skin and wrinkles. Exfoliation may offer some benefits because the process encourages skin-cell turnover, which helps shed potentially damaged cells before they can mutate. Add a peel to your routine to keep your surface layers fresh.
Above all else, a yearly check with your dermatologist is essential. That doctor's appointment will keep tabs on your skin so you don't end up blindsided by damage. And, it will help you nip suspicious spots in the bud — before it’s too late.