What You Need to Know About Sunscreen and Sun Safety: Fact Check with Dr. Larisa Geskin

August 11, 2021

Our relationship with the sun is tricky. The sun provides us with much-needed Vitamin D, a nutrient that helps strengthen our bones and prevents diseases like osteoporosis, and moderate sun exposure has been proven to enhance our moods, help alleviate stress, and improve our sleep habits.

The messaging can be confusing, says skin cancer specialist and dermatologist Dr. Larisa Geskin, who works to raise awareness of skin cancer prevention and sun safety. “People should enjoy being outdoors and spending time on the beach and in the sun, but you have to be protected.” 

Research image illustrating overview of UV and sunblock

Illustrates types of UV rays, their penetration, and effects on skin (Image: Sophie Geskin)

Sun exposure is a major risk factor for skin cancer, the most common form of cancer, with an estimated 9,500 people in the U.S. diagnosed each day. A small percentage of these diagnoses are melanoma, a form of skin cancer that is a potentially fatal disease. Today, melanoma is the fifth most common cancer among men and women, and recently there has been an increase in the incidence of melanoma affecting individuals aged 15 to 39 years.

To raise awareness for skin cancer prevention, Dr. Geskin and her colleagues in the Department of Dermatology at Columbia University Vagelos College of Physicians & Surgeons are always looking to share key facts on what the public should know about sun safety and sunscreen. Here’s what they had to say.

In general, who needs to use sunscreen and how often?

Everyone over the age of six months need to use sunscreen. Infants are at greater risk than adults of sunscreen side effects, such as developing a rash. Daily sunscreen is an important step to protecting against harmful ultraviolet (UV) radiation, and sunscreen should be reapplied at least every two hours. If swimming or sweating, sunscreen may rub off, so it needs to be reapplied more often.

The FDA and the American Academy of Pediatrics recommend keeping newborns and babies younger than six months out of direct sunlight. The best sun protection for these infants is to stay in the shade.

What exactly is broad spectrum SPF? Why does it matter and what’s the “correct” amount?

The sun emits ultraviolet radiation (UV) that we cannot see, consisting of three types of UV rays: UVA, UVB, and UVC. Only UVA and UVB pass through the atmosphere and these types of UV light are the key culprits in harming our skin. UVA rays make up 90 to 95% of UV radiation and are able to penetrate the two outer layers of the skin causing skin cancer, aging, and wrinkles. UVB rays penetrate the outermost layer of the skin and are considered the primary cause of sunburns and skin cancer.

SPF stands for Sun Protection Factor and measures how much protection a sunscreen provides from UVB rays. For example, correctly applying SPF 30 sunscreen will block 97% of UVB light for two hours, whereas SPF 50 and SPF 100 block 98% and 99% of UVB light, respectively. We typically recommend at least 50 SPF for daily skin protection, though people with fairer skin, lighter hair, or a genetic predisposition to skin cancer should consider using a higher SPF. 

Broad spectrum SPF is a designation that means a sunscreen protects against both UVA and UVB rays. This is the only way to adequately protect against the UV light types that cause skin aging as well as skin cancer. People should look for the label “Broad Spectrum SPF” on any sunscreen product to ensure they are using one that provides full sun protection.

What are key ingredients people should look for in their sunscreens and what are the differences between sunscreen, sunblock, or suntan products?

The term “sunscreen” typically refers to chemical sunscreens. These sunscreens contain active ingredients that absorb UV rays to prevent damage. Common ingredients include oxybenzone, avobenzone, octisalate, octocrylene, homosalate, or octinoxate. “Sunblock” usually refers to physical sunscreens. These act like a physical barrier, bouncing the UV rays off the skin and protecting the skin beneath from their harmful effects. The most important active ingredients are zinc oxide and titanium dioxide. Typically, we recommend patients use physical sunscreen with a cumulative zinc and titanium oxide concentration of >10% (better yet, approaching 20%!). Physical sunscreens work immediately after application, while chemical sunscreens take time to absorb. Physical sunscreens also are often better for those with sensitive skin.

When people say suntan products, they may mean different things. Creams or oils that are used before sun exposure to increase a suntan without providing any sun protection are clearly harmful. Some suntan products that are designated with an SPF less than 15 are inadequate, though they provide some sun protection. Sunless tanning products are dyes that make the skin look tan without sun exposure. These ingredients are safe but provide no sun protection.

Do people need to wear sunscreen indoors or while driving?

If you are anywhere near a window, you are likely getting exposed to UV radiation. Many windows provide protection from UVB light so you don’t easily get sunburned, but they do allow some UVA rays to pass through, causing skin damage. To best prevent premature photoaging and wrinkles, make sure to apply sunscreen indoors and out. 

What exactly is sufficient coverage and why does it matter?

Sufficient coverage of sunscreen is about 1 ounce (a shot glass amount) for the entire body, including the face. Areas not covered by clothing are especially important, including areas that we often forget about when applying sunscreen like the scalp and even the lips. This is important because sunscreen provides protection only when applied correctly and in sufficient amounts.

What are the top misconceptions about sunscreen? What else should we know?

Sunscreen alone is not a comprehensive sun safety strategy. Sunscreen will not block all of the sun’s UVA and UVB rays, even when applied correctly. Reapplying regularly, covering up with sun-protective clothing, seeking shade, and wearing a hat and UV-blocking sunglasses can all help protect you against burns and skin damage.

Recently, certain sunscreen products were found to contain contaminants that were unsafe, and voluntarily recalled. These have been removed from shelves, and all sunscreens currently stocked are undergoing rigorous testing to ensure their safety.

Contributors: Larisa Geskin, Bradley Kwinta, and Connor J. Stonesifer