How sex, sunshine and exercise makes us sneeze

As the dreaded flu season approaches you might want to consider this—research shows that a sneeze can travel up to 70cm and it can be caused by sunshine, exercise and even sex.

While the good folk at Massachusetts Institute of Technology (MIT) used a high-speed camera to measure how far mouth fluid travels during a sneeze, you don't need a science degree to know the phenomenon is not great news for those standing nearby.

Sneezing, or sternutation, is an instinctive immune response and happens when nerve endings, usually in the nasal lining, become irritated by particles such as dust, pollen or bacteria.

Signals from the brain tell the body to close the throat, eyes and mouth, while the chest muscles rapidly contract and the throat quickly relaxes, causing air, saliva and mucus to be expelled.

Stand back

Laden with droplets of bacteria, this sudden blast of aerosols travels like a cloud and is the most common transmitter of respiratory disease between people, Curtin University medical scientist Dr Trilochan Mukkur says.

"Even if you are a metre away you can still catch the disease [from someone sneezing] because the aerosols travel a fair bit," he says.

So, the sneeze is a bit of a mixed bag, while typically a sign of illness, it also functions in healthy people to ward off disease.

Sex on the brain

In 2008, British doctors discovered that orgasms, sex or even just thinking about intercourse causes some people to sneeze.

One middle-aged man described uncontrollable fits of sneezing with sexual thought, the doctors reported.

The research found the "under-reported" phenomenon may be genetically passed on and caused by a defect in the parasympathetic or unconscious nervous system.

The scientists concluded sneezing caused by exposure to light and having a full stomach, or snatiation, may also be linked to a nervous system glitch.

Up to one in four people sneeze due to sunlight.

Meanwhile, others suffer from exercise-induced rhinitis, where the body has an allergic reaction to exercise causing congestion, watery eyes and sneezing.

The condition is little-understood, but some scientists think it may be linked to heightened neural activity in the part of the brain involved with blood flow to the nasal mucosa, causing increased sensitivity to irritants.

There are many myths associated with sneezing, but you can be sure this winter that your eyes will not pop out or that your heart will not stop beating if you sneeze.

This article first appeared on ScienceNetwork Western Australia a science news website based at Scitech.