Photic Sneeze Reflex - Sneezing When You Look At the Sun 

Many stimuli can trigger a sneeze, such as colds, allergies, cold air, humidity, irritants such as pepper, eating too much, cooling certain parts of the skin, sexual excitement, hair pulling, shivering, eyebrow plucking, and as you’ll find here - exposure to bright sunlight. The Photic Sneeze Reflex (PSR) is otherwise known as sun-sneezing, photogenic sneezing or ACHOO. It occurs in about 25% of people and is a sneezing reflex that occurs when you move into the sunlight or other bright objects. It can be inherited from your parents.

Scientists have not yet discovered why this happens, but it might reflect a “crossing” of pathways in the brain, between the normal reflex of the eye in response to light and the sneezing reflex. This may also be the reason behind the sneeze that sometimes occurs when plucking your eyebrows.