Why do we get motion sickness?
The short answer
Motion sickness can happen when information about movement from your eyes, inner ear, muscles, and joints does not fit together. For example, in a moving car, your body senses bumps and turns while your eyes stay focused on a book. The brain receives signals that do not match, and this mismatch is thought to trigger motion sickness.
How does your body sense movement?
Deep inside the inner ear are organs that sense the movement and tilt of your head. The semicircular canals sense head rotation. Two other organs, called the otolith organs, sense tilt and movement forward, backward, side to side, or up and down. Your eyes show how the view around you moves, while muscles and joints send the brain information about your body's position.
The brain combines these signals to work out which way you are facing and how you are moving. It also uses past experience to predict what movement is likely to come next. The most widely accepted explanation for motion sickness is that symptoms can start when the signals coming in do not match the movement pattern the brain expects.
Why can reading or using a phone make it worse?
When you keep your eyes on a book or phone, you focus on a nearby, mostly still object and may not notice the view outside moving past. At the same time, your inner ear and body sense the car speeding up, braking, or turning. If the mismatch between these signals continues, you may start to feel unwell.
The mismatch can also work the other way around. In virtual reality or a moving video, your eyes may see motion that your body and inner ear do not feel in the same way. That is why motion sickness can happen even when you are not riding in a vehicle.
Why can it cause nausea and cold sweats?
Motion sickness can involve nausea and vomiting, but it may also cause dizziness, yawning, drowsiness, pale skin, and cold sweats. The brain's response to mismatched movement signals appears to affect several body functions. The detailed steps that lead from that mismatch to nausea are not fully understood.
Two people can react differently to the same ride. The strength of the motion, a person's sensitivity, and past experience can all matter. Repeated exposure to a particular kind of motion may help the brain adapt, but getting used to it can take time, and the change may not carry over to a different ride or pattern of movement.
What may help?
- Look at a distant view or the horizon, if you can.
- Take a break from reading or looking at a screen.
- Choose a seat with less movement and avoid large head movements.
- Get some fresh air when possible.
These steps may reduce the mismatch between what your eyes and inner ear sense, or reduce how much your body moves. They do not work for everyone or prevent every case. Some motion-sickness medicines can cause drowsiness, so read the label and ask a pharmacist or doctor if you are unsure whether a medicine is suitable.