What To Know About Sunscreen and Skin Cancer Prevention
Key Takeaways:
- Broad-spectrum sunscreens protect against both UVA and UVB rays, which is important because both types of UV radiation can contribute to skin damage and skin cancer
- SPF only indicates how well a sunscreen protects against UVB rays that cause sunburn. Higher SPF offers only modest additional protection, so broad-spectrum coverage is more important than simply choosing the highest SPF
- For the best protection, combine sunscreen with other sun-safe habits, such as wearing protective clothing, using a wide-brimmed hat, seeking shade and limiting time in direct sunlight
Summer is in full swing, and many people are spending more time outdoors. While sunscreen is an important part of protecting skin from harmful ultraviolet (UV) rays, choosing the right protection can be confusing with so many options on the shelves.
In a recent conversation, Moffitt Cancer Center President and CEO Patrick Hwu, MD, sat down with dermatologist and melanoma researcher David Fisher, MD, PhD, of Massachusetts General Hospital to discuss the science behind sun protection, what SPF really means and why broad-spectrum protection is key to reducing the risk of skin cancer.
#Sunscreen can be one of the most important tools for protecting your skin, but choosing the right one matters.
— Dr. Patrick Hwu (@PatrickHwuMD) July 29, 2026
I spoke with dermatologist and melanoma researcher Dr. David Fisher of @MassGeneralNews @harvardmed about why broad-spectrum protection against both UVA and UVB rays… pic.twitter.com/gYZVYHgpXU
Understanding SPF
Sunscreens are commonly labeled with sun protection factors, or SPF, but Fisher says it is important to understand what that number represents.
SPF measures how well a sunscreen protects against UVB rays, the portion of the ultraviolet light that causes a sunburn. The rating compares how much UVB exposure skin can tolerate before burning when wearing sunscreen versus when not wearing sunscreen.
“SPF is not a measure of cancer protection. It is quantified as a measure of sunburn protection,” Fisher said.
Patrick Hwu, MD
While higher SPF values provide additional protection, Fisher says the difference between SPF 30 and higher numbers, such as SPF 50 or SPF 100, is smaller than people realize. Rather than focusing only on the highest SPF available, he encourages consumers to choose a broad-spectrum sunscreen that protects against both UVA and UVB rays.
Why UVA Protection Matters
Although UVB rays are responsible for sunburn, UVA rays account for more than 90% of the ultraviolet radiation that reaches the Earth’s surface. Unlike UVB, UVA doesn’t typically cause an immediate burn, making it more difficult to recognize its effects on the skin.
However, Fisher says UVA exposure still damages skin cells and contributes to the development of skin cancer.
“While it is less potent than UVB in mutating the genome of our cells on our skin, it still does do that. And it unequivocally does produce mutations that are associated with skin cancer,” Fisher said.
Fisher also discussed new UVA-blocking ingredients that have expanded protection against UVA rays. Bemotrizinol is a sunscreen ingredient recently approved by the FDA that blocks UVA rays while remaining on the skin’s surface.
“It has sufficient physical properties of the molecule that seems incapable of penetrating deeply into the skin. Therefore, it is felt to be highly safe,” he said.
Sunscreen is One Part of Sun Safety
Sunscreen should be used alongside other protective measures to help reduce UV exposure. Hwu recommends wearing protective clothing and a wide-brimmed hat that helps shield parts of the body.
“Stay out of the sun, wear big hats, not just a cap, but the big hat with the rim all the way around, and cover up with clothes. But then, if you’re going to take a sunscreen, have one that can block both UVA and UVB,” Hwu said.
