The tendency to sneeze on

The tendency to sneeze on exposure to bright light is termed the "photic sneeze". It is a genetic character transmitted from one generation to the next and which affects between 18 and 35 per cent of the population. The sneeze occurs because the protective reflexes of the eyes (in this case on encountering bright light) and nose are closely linked. Likewise, when we sneeze our eyes close and also water. The photic sneeze is well-known as a hazard to pilots of combat planes, especially when they turn towards the Sun or are exposed to flares from anti-aircraft fire at night.