The sun face is an expression preformed involuntarily by one who is exposed to sun or other bright light. While subjected to light nature takes over and creates its own version of sunglasses causing the eyes to squint creating a wrinkled chink look. During this deep, intense squint a chain reaction occurs and the performers mouth will unknowingly creep open, and will also fall victim to a curled upper lip and flaring nostrils.
Sun faces are common among people driving in the sun, people waking up in the morning to bright light, and summertime power walkers. Although not confirmed by science the sun face is believed to be an effective form of birth control.