DENVER — Dermatologist Dr. Whitney High never goes anywhere without his trusty umbrella to block out the sun, and there's good reason.
"Cancer that's caused by the sun is the most common cancer of mankind," said High, a professor of dermatology and pathology at the University of Colorado who also practices at Denver Health and the UC Health system.
Many people already know a few of the basics of sunscreen use, including using at least one ounce of sunscreen for exposed skin, re-applying at least every two hours and looking for a sunscreen that has UVA and UVB protection.
"UVA is involved in things like photoaging or looking older than you should from sun exposure. UVB is more involved in skin cancer," said High.
Which SPF is best?
It's common for dermatologists to see people not applying enough sunscreen for the SPF to work as intended. When put on properly, SPF 30 blocks 97% of ultraviolet light. That number drops significantly when it's not put on correctly.
"If you're choosing SPF 70, and you're putting it on like an average person, you're probably getting about SPF 35," he said.
The SPF that's right for you depends on your complexion or sensitivity to the sun and how long you plan to spend outside.
"If you would burn in four minutes and you're wearing SPF 10, then you should be able to stay out 40 minutes without burning. It doesn't guarantee that you won't sunburn or anything like that. It just prolongs the time that you're able to stay in the sun," High said.
Chemical vs. mineral Sunscreen
When it comes to chemical and mineral sunscreen, High said the labeled SPF is equal across products, even though they work differently.
"Chemical sunscreens take solar energy and absorb it through chemical bonds," said High. "[Mineral] sunscreens, on the other hand, they act like little tiny mirrors, and the light that strikes your skin is reflected off.
However, people may have a preference depending on what ingredients their skin can tolerate.
"[Mineral] sunscreens are largely inert and wash off in the shower and things like that. The chemical sunscreen, some people worry about things like allergic contact dermatitis. You can become allergic to your sunscreen, or they worry about the chemicals penetrating the skin and leading to some other health issues," he said.
Do different complexions need different sunscreens?
Depending on a person's complexion, they may need to take more precautions or could get away with fewer precautions when it comes to sunscreen. However, when it comes to your skin's safety, High said it's not worth risking it.
"Different people produce different amounts of melanin that result in different physical appearances of the skin, and it also is more protective of the skin, too," he said. "People that have a darker skin type can probably use lower SPF and get the same effect, and they can probably also not apply as much or use it as frequently. But I don't necessarily want to embolden anyone. It's still great to follow the universal guidelines for sunscreen use."
How different exposure impacts your skin
When skin is damaged from the sun, the difference is obvious to a doctor when they look on a microscopic level.
The pink layer toward the bottom of the picture is what healthy skin cells should look like. The upper, tightly clustered gray area is solar elastosis, a sign of heavy sun damage.
"This is many, many, many years of sun damage," High said. "This is kind of continual sun damage on weekends or even during the weekdays if they work in the sun, and it's resulting in this kind of sun damage."
Next, High showcased an example of the most common cancer of humans: basal cell carcinoma.
The clusters of purple dots indicate the cancer. This patient did not have a job or lifestyle that had them consistently exposed to the sun. High described this patient's exposure as similar to that of a weekend warrior who loves getting outside on their day off but without sun protection.
"Even if you're not outside constantly, but you're getting too much sun intermittently. You enjoy water skiing or skiing outdoors in the winter time where it's bright sun and elevation, all those things can cause intermittent, heavy solar damage, which is more tightly associated with melanoma and basal cell carcinoma," he said.
Melanoma, the most deadly kind of skin cancer, looks like this:
"The melanoma grows from the junction of the epidermis, the outer layer of the skin, and the dermis and grows into the skin," said High.
This type of cancer can be noticed in the changing of moles in size or shape.
"Melanoma, like basal cell carcinoma, is a cancer that's associated with that intermittent weekend warrior type of personality, where you're out in the sun a whole lot. Melanoma also has a familial component to some cases, and that's why we ask questions at the doctor's office about whether you have a first-degree relative with melanoma," he said.
Year-round sun exposure tips
When spending time outdoors, High said the most cancer-causing wavelengths, UVB, hit around 10 a.m. to 2 p.m. Do not skip sunscreen during those hours or try to take a break from your outdoor plans during that time.
Cloudy days do not offer proper sun protection.
"Clouds only absorb about 20% of the ultraviolet light that strikes the Earth. So you still need to wear sunscreen on cloudy days, too. You need to be cognizant that even if most of you is covered up, things like water and snow can reflect light back at you," said High.
A good reminder for those new to Colorado — the altitude can cause a sunburn faster without proper protection.
"You're closer to the thinner atmosphere, and a greater amount of atmosphere would have filtered more of that ultraviolet light," he said.
