Which sunscreen should you choose, though? For starters, the American Dermatology Association (ADA) recommends one that's labeled “broad-spectrum,” because this means it protects against both UVA and UVB rays. UVA rays are the ones that prematurely age your skin, causing wrinkles and age spots, while UVB rays cause sunburn. Overexposure to both can lead to skin cancer. Next, consider the Sun Protection Factor (SPF) SPF is a measure of how much UVB light a sunscreen can filter out. Dermatologists recommend using an SPF of at least 30, which Adarsh Vijay Mudgil, MD, a dermatologist practicing in New York, calls "the magic number". SPF 15 blocks about 93 percent of UVB rays, while SPF 30 blocks about 97 percent of UVB rays. The ADA recommends an SPF of 30 or higher. It's important to apply enough sunscreen to any exposed area of skin every day. On days you're going to be outdoors for an extended period of time, say playing golf or at the beach or pool, Mudgil suggests putting a base coat of SPF 30 all over the body a half hour before leaving the house and then reapplying every two hours. If you're swimming, Mudgil says it's a good rule of thumb to grab the sunscreen every time you get out of the water. Remember, no sunscreen can completely protect you from sun so it's important to always reapply throughout the day, wear protective clothing (hats, sun-protective swimwear, clothing, etc.) and always seek shade. Pay attention to your skin type as well “If you have acne or oily skin, make sure that your sunscreen is labeled as ‘non-comedogenic,’ which means that it has been shown not to block pores,” says Joshua Zeichner, MD, director of cosmetic and clinical research, dermatology department, Mount Sinai Hospital. “If you have dry skin, look for moisturizers with sunscreen or sunscreens that contain hydrating ingredients.” (Think: hyaluronic acid or ceramides.) For sensitive skin, opt for a physical, or mineral, sunscreen, says Emily Smith, MD, dermatologist at University of Missouri Health Care. Physical sunscreen features zinc oxide and titanium dioxide to protect skin; these two ingredients won’t burn or sting eyes, Smith says. They sit on top of your skin, forming a barrier to protect you. Source: https://www.nbcnews.com/better/lifestyle/how-choose-best-sunscreen-according-these-dermatologists-ncna1002451#anchor-Payattentiontoyourskintypeaswell