Ep 135: Why do I sneeze at the Sun?

Do you sneeze at the Sun? I do. My brother does. Both my parents do. In fact, we are a family of Photic Sneeze sufferers. The Photic Sneeze Reflex (PSR), also known rather ridiculously as Autosomal Dominant Compelling Helioophthalmic Outburst (ACHOO) Syndrome (how long do you think it took researchers to figure out that acronym...) is a dominant genetic condition affecting around 10% of the population. When a sufferer moves from a region of darkness to a region of bright light - for instance, walking outside and looking at the Sun - multiple sneezes occur. Researchers into the disorder have yet to explain either its mechanism or an evolutionary reason for why it occurs. One theory is that there is a "short circuit" in the brain, with the stimulated optic nerve somehow triggering the sneeze reflex. Professor Louis Ptáček runs the Laboratories of Neurogenetics at the University of California, San Francisco. The aim of the lab is to study familial disorders with strong genetic contributions, and thus localise and identify genes that cause human disease. Other conditions in which he is interested include migraine and epilepsy, and an intriguing condition whereby certain sounds cause seizures. He considers PSR to generally be a midly annoying condition, unless you are a combat pilot, where sneezing at the Sun could indeed be life threatening. I had a really interesting chat to Louis about PSR, and I've left the recording a little longer than usual, as we were really able to explore some fascinating ideas involved with PSR - it was a great chat. This topic came in as part of my call for questions for Science Week, so thanks @lisushi for the question! I'll be putting up more blogs and podcasts to answer the other questions that came in over the next few weeks.