Have you ever stepped out on a sunny day only to be struck by a bout of sneezes? If yes, you likely suffer from a rare genetic condition that has been baffling scientists for millennia. Photic sneeze reflex—also known as autosomal compelling helio-ophthalmic outburst, or ACHOO—affects 10% of the world’s population. Scientists from Aristotle to Francis Bacon have had their own conjectures about the syndrome, but modern science has proved all these theories wrong. As scientists today continue to try to solve the ACHOO effect, the answer might not be as simple as you think.
