Do you sneeze after seeing bright light? Well, you're not alone. ACHOO syndrome, or Autosomal Dominant Compulsive Helio-Ophthalmic Outbursts, is estimated to affect between 18–35% of people around the world. While not a dangerous condition, it is one that continues to mystify scientists.
Records of ACHOO syndrome have been found as far back as 350 BCE. Unlike regular sneezes, which occur after the mucous membranes in our nose are irritated by particles, there is no physical trigger other than bright light. This can happen outdoors in the sunshine, or inside after turning on the light. “The reflex seems to be triggered by a change in intensity of light rather than a specific type or wavelength of light,” Dr. Annie Nguyen, an ophthalmologist with Keck Medicine of USC, says.
Although scientists know that ACHOO syndrome is genetic, they are still unsure what causes it. One previous theory suggests that bright light which makes the pupils constrict also irritates the nose. Another proposes that it's due to higher sensitivity to visual stimuli.