A well-formulated sunscreen will prevent tanning or the deepening of skin’s color as it works to shield skin from the harmful rays responsible for triggering that response. However, research shows that user error in under-applying sunscreen is still prevalent both in the United States, as well as many other countries, which could mean you may still see a tanning effect or sunburn on skin even after applying SPF (2). One of the biggest mistakes that most people make is not applying/reapplying sunscreen liberally enough to achieve adequate protection.