What is an SPF rating anyway?
SPF, or Sun Protection Factor, is a measurement of how well a sunscreen will protect skin from UVB rays, the kind of radiation that causes sunburn and is thought to contribute to some types of skin cancer. Example: If your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen would allow you to stay in the sun without burning for approximately 150 minutes (a factor of 15 times longer). This is a rough estimate and depends on skin type, the intensity of sunlight, and the type of activity. But SPF isn’t quite that simple. The scale is not linear: SPF 30 actually only blocks 5% more UVB radiation than SPF 15. For best protection, experts do recommend a minimum SPF rating of 15, and applying sunscreen generously and frequently. The SPF rating only tells you only about UVB protection, not about harmful UVA rays. UVA is the wavelength of sunlight that penetrates deeper into the skin without causing surface burning, but has the potential to release free radicals a
