The recommended SPF number you are looking for is in the SPF 15 to SPF 30 range,” says Dr. Orit Markowitz, a dermatologist and skin cancer specialist at Optiskin Medical in New York City. “The key with SPF is proper application. I recommend my patients wear SPF 30 and reapply every two hours.”  Most tanning oils don’t come in formulations above SPF 15, says Dr. Daniel Belkin, a New York City-based cosmetic dermatologist—it kind of defeats the purpose. “A traditional tanning oil will likely not have an SPF over 15 because the goal is to enhance penetration of UV rays and not protect from them.