What causes motion sickness—and how can you prevent it?

For some travelers, a catamaran sail off Oahu, Hawaii, or a camel ride through the desert in Morocco isn’t an enviable vacation experience. It can cause nausea, dizziness, and chills.

Motion sickness like this can happen to almost anyone, including children and dogs. Studies suggest that more than half of all people who ride in automobiles experience carsickness. Recent surveys of members of the Indian Navy, Icelandic fishermen, and South Carolina marine biologists indicate that up to 80 percent of individuals who work on boats get seasick sometimes.

“We’re even seeing cybersickness now, with people looking at their phones when riding in the car or wearing glasses for a 3D movie,” says Andrea Bubka, a professor of psychology at Saint Peter’s University in New Jersey, who has extensively studied motion sickness.

Here’s why motion sickness happens and what travelers can do to prevent it.

What causes it

Scientists aren’t sure why some people feel nauseated the second they step on a boat, while others can blithely read long novels while riding in the backseat of a car. They do have some theories.

Many scholars believe that motion sickness is caused sensory conflict, a difference between what people see and the sensations they feel. “Human beings did not evolve to travel in space shuttles and use virtual-reality video games,” says Marcello Cherchi, a neurologist at Northwestern University’s Feinberg School of Medicine.

Sensory conflict happens when your body feels the heaving of an ocean ferry or the jolting motion of a bus winding through the mountains and your eyes, ears, and other senses can’t catch up. It can cause symptoms such as dry mouth, dizziness and a pounding headache.

However, other scientists believe that people get motion sick because they don’t instinctively change how they sit, stand, or walk in a moving mode of transport. That disconnect causes you to feel ill.

One of the biggest proponents of this “postural stability theory” is Tom Stoffregen, a professor of kinesiology at the University of Minnesota. He says that you must learn to move differently on a boat or plane. This is similar to sailors who learn to get their “sea legs” after a few days. “The key is physical control of your body, and some individuals adapt more quickly than others.”

Genetics might play a part, too. A 2015 study of 480,000 customers of DNA-testing company 23andme identified 413 genetic markers–many related to balance or eye, ear, and cranial development–that could make an individual predisposed to motion sickness.

Preventing motion sickness

The easiest way to combat motion sickness is to prevent it from happening in the first place. You can hydrate and keep fresh air flowing by opening a window, turning on the air vents above you on the plane, or going to the deck of a cruise ship.

“Be careful what you eat while you travel,” Bubka says. Motion can amplify any issues that you have on dry land, such as eating too much or too little, excessive alcohol consumption, or excessive caffeine intake.

“Do everything you can to be sure your view isn’t obstructed,” says Natascha Tuznik, a doctor who specializes in travel medicine at the University of California Davis. “Look out at the horizon if your are looking out to sea, and then sit in front of the car so you can see the road ahead and what’s coming. This will help your eyes and inner ears connect more quickly with other bodily functions.

Avoiding triggers and anti-nausea training

Some research suggests that doing physical or mental exercises could help humans train themselves to be less motion sick. The Puma Method, developed by a flight surgeon to serve airsick pilots, uses yoga-like stretches and angular movements to build up anti-nausea conditioning. A 2020 study at England’s University of Warwick found that, after doing 15-minute visuospatial training exercises (finding hidden objects in puzzles, folding paper), many subjects didn’t get sick when taken for car rides. Cherchi says that these methods don’t require medication. “The disadvantage is that they can entail considerable discomfort, at least initially.”

People prone to motion sickness can also practice “trigger avoidance,” steering clear of activities that make them bilious. Renting a car is a better option than long bus rides. You can then drive or sit in the front. People with seasickness should choose flat-water river cruises, or larger oceangoing ships that offer smoother rides.

Medication–or gadgets–might help

Another way to combat travel-related nausea? You can also use an over-the-counter medication for motion sickness (such as Dramamine) or a doctor-prescribed Scopolamine patch (usually worn behind your ear). Both anticholinergics block and inhibit the central nerve system to calm the stomach and bowel muscles.

However, these medicines only work if used a short time before you set sail or board that flight. These drugs can make you feel groggy and some people have medical conditions that prevent them from being used. Stoffregen suggests that travelers who don’t wish to take pills try ginger chews and gingersnaps. “There’s well-documented evidence that a little bit of ginger can significantly reduce nausea,” he says.

Multiple gadgets promise to help with motion sickness. Pressure-point wristbands, which rely on acupressure principles, come in models from inexpensive and basic to high-tech and high-priced. Wacky-looking anti-nausea glasses also came to market about two years ago, sporting liquid-filled frames and four round, glass-free lenses. The idea behind the glasses is that the liquid in them shifts with your movements, creating an artificial horizon.

While many users report feeling better when using these devices on planes, trains, and automobiles, studies have yet to support their efficacy. Stoffregen says, “But, if there is a placebo effect and you don’t become sick, then I don’t care about science.” “It’s money well spent.”

Jennifer Barger is a senior travel editor at National Geographic. Follow her on Instagram.