SPF: What It Really Means for Sun Protection and Skin Health

When you see SPF, Sun Protection Factor, a measure of how well a sunscreen blocks UVB rays that cause sunburn. Also known as Sun Protection Factor, it's the number on the bottle that tells you how long you can stay in the sun before your skin starts to burn — but only if you apply it correctly. Most people think SPF 30 is twice as good as SPF 15, but that’s not true. SPF 30 blocks about 97% of UVB rays. SPF 50 blocks about 98%. The jump from 30 to 50 isn’t doubling protection — it’s adding one extra percentage point. What really matters isn’t the number, it’s whether you’re using enough, reapplying often, and covering every exposed spot.

SPF only measures protection against UVB rays, the ones that burn your skin. But UVA rays are just as dangerous — they go deeper, age your skin, and contribute to skin cancer. That’s why you need broad-spectrum sunscreen, a formula that protects against both UVA and UVB radiation. Look for it on the label. If it doesn’t say broad-spectrum, it’s not enough. And don’t forget: sunscreen isn’t the only tool. UV radiation, invisible light from the sun that damages skin cells and increases cancer risk doesn’t care if it’s cloudy, snowy, or you’re sitting by a window. It still gets through. That’s why daily protection isn’t optional — it’s a habit, like brushing your teeth.

People who skip sunscreen because they’re not at the beach are making a mistake. Daily exposure adds up. A study from the Journal of the American Academy of Dermatology showed that people who use sunscreen every day reduce their risk of melanoma by 50%. That’s not a small number. It’s life-changing. And it’s not just about cancer. UV damage causes wrinkles, dark spots, and broken capillaries — the kind of stuff you can’t fix with creams. The right SPF, used right, slows that down. You don’t need expensive brands. You don’t need fancy labels. You just need something that says SPF 30 or higher, broad-spectrum, and water-resistant if you’re sweating or swimming. Apply a shot glass full for your whole body. Reapply every two hours. And if you’re on medications like antibiotics or retinoids that make your skin more sensitive? SPF isn’t a suggestion — it’s your shield.

Below, you’ll find real-world advice on how to use sunscreen safely, what to watch out for when combining it with other meds, and how sun exposure connects to conditions like pterygium and skin cancer. These aren’t theory pieces. They’re guides written by people who’ve seen the damage — and the solutions — firsthand.