The numbers on sunscreen, known as the Sun Protection Factor (SPF), indicate the level of protection the product offers against UVB rays, which are primarily responsible for sunburn and can contribute to skin cancer. For example, an SPF of 30 means that theoretically, it would take 30 times longer for your skin to burn than if you were not wearing any sunscreen.
Here’s how SPF works:
- SPF 15 blocks about 93% of UVB rays.
- SPF 30 blocks about 97% of UVB rays.
- SPF 50 blocks about 98% of UVB rays.
Higher SPF numbers do provide slightly more protection, but the difference becomes minimal beyond SPF 30. It’s also important to note that no sunscreen can block 100% of UV rays.
Additionally, the effectiveness of sunscreen can be affected by factors such as skin type, the amount applied, and how often it is reapplied, especially after swimming or sweating. Therefore, it’s recommended to use a broad-spectrum sunscreen with at least SPF 30 and to reapply every two hours or immediately after swimming or sweating.
