Beyond SPF: what really keeps your skin safe in the sun
Dermatologists say consistent sunscreen use — not higher SPF numbers — is key to protecting skin from harmful ultraviolet radiation, as more Americans head outdoors during warmer months.
Dr. Victor Quan, a dermatologist at Northwestern Medicine, told Straight Arrow sunscreen with SPF 30 already blocks about 97% of UV rays, compared with about 98% for SPF 50.
“Higher SPF doesn’t get you that much more protection,” Quan said, emphasizing that proper use matters more than the number on the label.
Instead, he said effectiveness depends on how consistently sunscreen is applied and reapplied. “No matter what SPF, it’s essential to reapply at least every two hours for it to work,” he said.
That guidance aligns with broader advice from dermatologists nationwide. Dr. David Y. Chen of Barnes-Jewish Hospital told Straight Arrow ultraviolet radiation plays a major role in skin cancer development.
“We know that any skin cancers, a large part of why they develop is because of some of the harmful ultraviolet light that comes in contact with the skin and forms mutations that ultimately contribute to cancer,” Chen said.
Experts say sunscreen should not be treated as a one-time application. Chen said it should generally be reapplied every 90 minutes to two hours, especially during prolonged outdoor exposure.
Quan echoed that message, adding that even water-resistant or sport sunscreens require regular reapplication.
“They may feel stickier, be harder to wash off, or can sometimes make your eyes sting,” Quan said, noting that those formulations are designed to stay on the skin longer but are not permanent.
Cost is another common concern, but Quan said price does not determine effectiveness.
“There is no difference in effectiveness for sun and UV protection,” he said of sunscreens with the same SPF level.
Higher-priced products may offer advantages such as improved texture or added moisturizers.
“Worth the money if you are more likely to use it,” Quan said.
Quan also addressed differences between mineral and chemical sunscreens. Mineral products typically contain zinc oxide or titanium dioxide and are less likely to irritate sensitive skin.
Chemical sunscreens, which are often lighter and used in daily moisturizers, may be more cosmetically appealing, but can occasionally cause irritation.
“There is some evidence that we absorb some small amount of chemical sunscreen, but there is no evidence that this is dangerous,” Quan said.
At the same time, dermatologists caution against misinformation about sunscreen circulating on social media, emphasizing that proven prevention strategies remain the most effective tools.
Ultraviolet radiation has both benefits and risks, Quan said. While it helps the body produce vitamin D, it can also damage DNA in skin cells, increasing the risk of aging and cancer.
“The truth is UVA also increases skin cancer risk and increases hyperpigmentation,” he said, adding that both UVA and UVB contribute to long-term skin damage.
Ella Rae Greene, Editor In Chief
