Sunscreen usage is climbing, but so are melanoma and skin cancer rates, and this, researchers say, is the “sunscreen paradox.” “The problem is that people use sunscreen as a ‘permission slip’ to tan,” said Dr. Ivan Litvinov, an associate professor in the Department of Medicine and Chair of the Dermatology Division at McGill University. Litvinov is co-author along with Dr. Sandra Peláez, Dr. Richie Jeremian and Dr. Pingxing Xie of two recent studies that explore the sunscreen pa...