What Causes Motion Sickness?
Also known as getting seasick, airsick or carsick, many of us get extremely ill when using these different forms of transportation. For those who are extremely susceptible to motion sickness — cases where medication fails to provide relief — most forms of recreation and travel are completely avoided.
But what’s the science behind it? Why does being on the water or flying in an airplane cause us to get physically sick?
What is Motion Sickness?
Motion sickness, also known as travel sickness, is a condition caused by the difference which exists between a person’s visually perceived movement and the vestibular system. The vestibular system is the part of your body which is responsible for spatial orientation, movement and balance. The most common signs and symptoms of motion sickness are dizziness, fatigue, and nausea. It’s no surprise that ‘nausea’ in Greek means seasickness (naus means ship).
Roughly 33% of the population is susceptible to motion sickness even in mild cases such as being on a boat in calm water, and 66% of us are susceptible in severe conditions.
So What Causes Motion Sickness?
A part of the brain – called the ‘area postrema’ – is responsible for both inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When you feel motion but don’t see it, your inner ear tells this part of the brain that it senses motion, but the eyes tell it that everything is standing still. As a result of the discrepancy, your brain will will think that one of them is hallucinating and that the hallucination is due to poison or neurotoxin ingestion. The brain responds by inducing vomiting to clear the supposed toxin or poison. In short, motion sickness is caused by your body believing it is being attacked by a neurotoxin or poison.
Space sickness was mostly unknown during the first spaceflights because astronauts were in extremely cramped conditions. Space sickness seems to be aggravated by being able to freely move – or float – around. Since there is more room in the shuttle and in the space station, space sickness is now more common. Roughly 60% of all Space Shuttle astronauts experience it on their first flight into space. The first case is believed to be attributed to Gherman Titov. In 1961, onboard the Vostok 2, Titov reported dizziness and nausea. The first severe cases were documented in the early Apollo flights. Frank Borman on Apollo 8 and Rusty Schweickart on Apollo 9 both reported experiencing identifiable and reasonably severe symptoms which eventually caused the mission plans to be modified.
Several forms of treatments exist for motion sickness. One common method is to simply look out of the window of the moving vehicle and to stare toward the horizon in the direction of travel. This will help to re-orient your inner sense of balance by providing visual reaffirmation of motion. At night, or in a vehicle without windows, it is suggested to close your eyes or take a nap. This will resolve the input conflict between your eyes and the inner ear. Napping can also help prevent psychogenic effects (sickness being magnified by thinking about it).
There is OTC and prescription medications also available for mild to moderate cases of motion sickness. These include Dramamine, Stugeron, and Antivert. Scopolamine is also effective for motion sickness and is used in the form of a transdermal patch.
Fun Fact: Individuals and animals without a functional vestibular system are completely immune to motion sickness.