Dermatologists Recommend SPF 30 Minimum as SPF 100 Blocks Only About 99% of UVB Rays
Updated
Updated · PBS NewsHour · May 30
Dermatologists Recommend SPF 30 Minimum as SPF 100 Blocks Only About 99% of UVB Rays
4 articles · Updated · PBS NewsHour · May 30
SPF 30 should be the minimum sunscreen choice, dermatologists said, because it offers strong protection and leaves more margin for the common problem of underapplying sunscreen.
SPF numbers measure protection against UVB rays, not total sun damage: SPF 30 filters about 97% of UVB, SPF 50 about 98%, and SPF 100 about 99%.
Broad-spectrum sunscreen is still essential because SPF does not reflect UVA protection; water-resistant formulas are recommended for swimming or heavy sweating.
Every 2 hours, sunscreen should be reapplied — or sooner after swimming or sweating — since higher SPF can create a false sense of security and does not justify longer sun exposure.
10 a.m. to 4 p.m. are peak UV hours, and experts said sunscreen works best alongside hats, sunglasses and sun-protective clothing.
If modern sunscreens can last up to eight hours, is the two-hour reapplication rule now an outdated myth?
Mineral vs. chemical sunscreen: Which type offers superior protection against aging, and is one genuinely safer for long-term use?
With a 2026 report finding most sunscreens unsafe, how can we confidently choose a product that actually works?