Taking a look at the science of sneezing

IT'S my birthday today, and I can tell I'm getting older - I've reached that stage in life where a good sneeze is enough to crick my neck or hurt my back.

Speaking of sneezing, did you know that the average person sneezes up to 450 times a year? That means I've probably managed to rack up upwards of 16,000 sneezes so far in my lifetime (with hopefully many more years of sneezing to come).

Why are we so sneezy? The explosive expulsion of air that we know as a sneeze is caused by irritation to our nasal mucous membrane.

Whether it's dust, pollen, or pepper, these small particles travel into our nasal cavity, where they initiate the release of histamine from cells. This histamine acts as a neurotransmitter, sending signals along your nerves and setting off a sneeze. This sends mucous flying out of your mouth and nose, along with all those irritating particles.

Here's a few fun sneezing facts. Closing your eyes is an involuntary reflex that happens when you sneeze. However, it is actually possible to sneeze with your eyes open (and no, your eyeballs won't pop out of your head).

We usually sneeze in groups - a single sneeze isn't always enough to get all the irritants out, but three or four might do the job.

A sneeze travels further than you think, with droplets travelling up to eight metres, and staying suspended in the air for as long as 10 minutes.

My favourite sneezing fact, though, is that sunlight makes some people sneeze. It's called photic sneezing, and happens in response to exposure to bright light, such as walking from a darker building into a bright sunny day. There's a lot of debate as to what causes it. Many researchers studying the phenomena suggest that it is a genetic condition, a result of having a slight variation in a gene compared to non-photic sneezers. Regardless of cause, scientists have come up with an excellent name for it. It's known as Autosomal Compelling Helio-Ophthalmic Outburst (or ACHOO) syndrome. And who says scientists don't have a sense of humour?

You might think it odd that scientists have spent so much time studying something as mundane as a sneeze.

But understanding more about sneezes has helped us understand more about the spread of infectious disease.

Now that we know how far a sneeze can spread, we understand why it's important to cover up when sneezing.

Dr Mary McMillan is a lecturer at the School of Science and Technology, University of New England