The Science Behind Motion Sickness and How to Prevent It

Motion sickness happens when sensory information conflicts between the eyes, inner ears and muscles and joints. Look at the true visual horizon, avoid tilting your head into turns, and get enough sleep to help reduce symptoms.

The nauseating feeling of motion sickness can strike on any kind of trip, from amusement park rides to virtual reality experiences. It can progress to a cold sweat, dizziness and vomiting.

The Eyes

When a person is experiencing motion sickness, their eyes, ears and body can’t catch up to what the brain is telling them. The resulting sensory conflict triggers symptoms like nausea, dizziness and vomiting. While scientists aren’t sure why some people experience motion sickness, they do know that there are things they can do to help prevent it.

The inner ear contains special receptors called vestibular (say: VEE-bular) cells that sense linear acceleration and angular acceleration in 3 different planes. These cells send information to the brain via the vestibular nerve. The brain then translates the information into an image that the eye sees. When the information being received from the visual and vestibular systems is in agreement, symptoms of motion sickness are suppressed. However, when there is a mismatch between the information being received and what is expected, symptoms of motion sickness occur. This has been referred to as the sensory conflict theory of motion sickness, and it is believed that this theory explains why some people get carsick while others don’t.

It’s thought that the reason why some people get motion sickness is because the information being received from their vestibular receptors is in agreement with the visual input, but the brain expects to be receiving different, and contrasting, sensory data. This is why some people feel motion sick when they are in a wide-screen movie theater, on a ride at an amusement park or during a virtual reality video game.

Another possibility is that the body can’t handle both types of movement. That’s why it is recommended that people who are susceptible to motion sickness try to look at a distant object, such as the horizon, while they are on a boat or airplane. In addition, the authors of one study have reported that a person can avoid seasickness by sitting on deck rather than inside, and by looking at the horizon while traveling in a car.

There are also over-the-counter drugs that can be used to combat motion sickness. These medications usually include scopolamine, which is a patch that is worn behind the ear. The main side effect of these drugs is drowsiness, so it is advisable to only take them as needed, and with the advice of your doctor or pharmacist.

The Ears

The first step in motion sickness is a problem with the sense of balance (vestibular) and spatial orientation. Our bodies use three different sensory systems to send information about body posture and movement to our brains: the inner ear, which detects head movements; our eyes, which register visual movement; and our neck, spine, muscles and joints, which sense a change in position. When the vestibular system signals that you are moving while the visual and proprioceptive systems tell you you’re sitting still, a conflict occurs that triggers nausea and vomiting. This is why you get sick on a tilting Tilt-A-Whirl ride, a swaying sailboat or a curvy road.

Our eyes see trees passing by, our ears perceive a swaying ship or the wind in your hair, but our inner ear also registers the motion of the earth beneath us. This is why the eyes are a big part of what makes us motion sick.

Scientists used to believe that people were divided into two categories: “head responders,” who primarily experience headache and drowsiness, and “gut responders” who mainly feel nausea and vomiting. But now researchers know that it is the interaction of provocative stimuli, relative susceptibility and previous experience that determine whether you will experience head symptoms or gut ones. It’s also possible that genetics play a role. A 2015 study of 480,000 customers of DNA-testing company 23andme found that there are more than 400 genes related to the eyes, ears and cranium that can predispose people to motion sickness.

You can reduce the chance of getting motion sickness by looking at something fixed on the ground in front of you, such as a horizon or the floor of your car. It is also helpful to sit where there is the least amount of motion, such as in the front seat of a car, on the center line of a bus or over the wing of an airplane. Over time, slow, intermittent exposure to motion can help prevent the onset of nausea and vomiting, so it’s best to spend a day acclimating to boating, for example, before you go out on the open ocean.

The Muscles

The brain gets conflicting signals from motion-sensing parts of the body. For example, the eyes see trees moving past and register movement while the inner ears sense stillness and the muscles and joints feel a different kind of movement. When these systems send conflicting messages to the brain, it gets confused and that is when motion sickness happens.

Anyone who has ever felt sick on a boat, amusement park ride or car trip knows that the sensation is not pleasant. Fortunately, it can be prevented or relieved.

Scientists are not sure what triggers motion sickness, but it is probably a mismatch between visual and sensory information about one’s body position in space. This information comes from the vestibular system, which is responsible for coordinating balance and sensing motion. It is believed that motion sickness occurs when the head is in an unfavorable position for the motion, the person has not adapted to that motion and there are other inputs from proprioceptive (body-position) sensors that cause nausea.

In addition, a person may experience a strong emotional reaction to the motion that leads to vomiting. In some people, this is the most prominent symptom of motion sickness. Other symptoms include cold sweating, yawning and fatigue.

Some medications, such as scopolamine, can be used to prevent motion sickness by applying it transdermally several hours before the anticipated stimulus. Antihistamines, especially first-generation drugs, can also be effective. However, they are sedating and can have adverse side effects. Other behavioral strategies that can be utilized to reduce the likelihood of motion sickness include watching the true visual horizon, steering the vehicle or tilting one’s head into turns and lying down with eyes closed.

People with a history of motion sickness are at increased risk for it in the future. It is important to know if you are susceptible to this condition so that you can take precautions before traveling. For most people, avoiding difficult conditions that will make them ill will eliminate or lessen their sensitivity to motion and a thorough medical history should be obtained to rule out other causes of the symptoms such as vestibular disease or migraine – especially to hamper things like a possible labor shortage impact.

The Brain

You get motion sickness when your brain receives conflicting information about your movement in space. This can happen when the inputs from your vestibular system, your eyes and non-vestibular proprioceptors are at odds with each other or differ from what you would expect based on past experience.

For example, on a moving ship, your eyes see the waves move past you and your inner ear tells you the ship is rolling. These different messages confuse your brain, resulting in nausea and vomiting.

The exact mechanism of motion sickness is unclear, but it involves excessive stimulation of the vestibular system (either angular motion signaled by the semicircular canals or linear acceleration from the otolithic organs) and the activation of emetic pathways in the brain (via the lateral septum, hypothalamus, area postrema of the medulla oblongata, vomit center and emetic chemoreceptor trigger zone). These chemoreceptors are similar to those activated after ingestion of food poisoning.

Symptoms can range from dizziness and nausea to sweating, fatigue and headache. Some people are particularly susceptible to motion sickness, including children and pregnant women. Those with balance disorders, especially benign paroxysmal positional vertigo, are also at risk. Some medications, like metoclopramide and ondansetron, can make motion sickness worse, so they should not be taken before or during travel.

The good news is that you can learn to become less sensitive to motion sickness. There are many treatment options, ranging from H1-antihistamines and anticholinergics to acupressure wristbands and other forms of desensitization. You may need to try a few different approaches to find what works best for you. A physical therapist experienced with vestibular therapy is an excellent resource for this. Gradually exposing yourself to the motion-triggering activity over time will help desensitize you and reduce your symptoms. As an alternative to medication, acupressure techniques are safe, inexpensive and have few side effects. They can be done at home or in a professional setting. If your symptoms persist, see your physician for advice. They can prescribe a different medication or provide other recommendations.