Car sickness: the surprising complexities of a common travel ailment

Laurie Mazer and her kids are are excited about heading to Massachusetts for a summer trip. But they’re less excited for the car ride.

“I throw up,” said Aine, Mazer’s two-year-old daughter. 

It feels yucky, she said.

During a five-hour trip about a month ago, her older brother Diarmuid recalls how she puked, twice, within the first ten minutes of hitting the road.

“Oh yeah, she throwed up on the bridge the first time,” he recalled.

“In my carseat. And on my blankey!” Aine clarified.

Thankfully, traffic was light. The family pulled over and cleaned up. But then on the way home, Aine threw up again.

“It was all made up of fruit, right?” said Mazer, the mom, to a nodding daughter. “So it was bright pink because it had lots of blueberries in it.”

Motion sickness can seem like a straightforward ailment, often synonymous with road trips and family vacations, yet how it works and what causes it is complicated. It has even been the subject of some debate.

A sensory mismatch

The conventional theory is that motion sickness is due to a sensory conflict.

“It’s when people are either getting too much motion or they’re getting motion that conflicts with another sense that’s telling them how fast they’re moving,” said Dr. Timothy Hain, a neurologist with Chicago Dizziness and Hearing, and a professor at Northwestern University.

Hain says most people, when put through enough motion, will vomit. Setting that scenario aside, the main thing that makes some get nauseated is when there’s a conflict between movement and one of our senses.

You might see that you’re sitting still in the car, for example, but you hear the car zooming down the highway and sense the bumps.

To get more specific, Hain says imagine sitting in the back of a car, looking at your cell phone. Your inner ear, the part of your body that helps regulate balance, is registering that you’re moving. But your eyes, perhaps locked on that cell phone, send signals that everything else is still.

“So there’s a sensory conflict between the eye and the ear,” said Hain.

Expectations don’t match, somehow making you nauseous.

Hain points to another example, way above the car, in outer space. Lots of astronauts get sick (even the best of them).

“These people who were so great on the ground and very great with flying jet airplanes, when they’re up in outer space, they have a new sensory situation, and the parts of their ear that sense gravity are totally irrelevant because there’s no longer gravity to sense,” said Hain.

They can’t tell which way is down.

“So this causes a horrible sensory conflict,” he said.

And potentially, horrible puking.

A mystery

People whose inner ear or vestibular system is totally damaged are immune to motion sickness, but beyond that, who actually gets sick varies.

Kids and women appear to be more prone to it. Same goes for people who get migraines.

But why is somewhat of a mystery.

Some have suggested genetic differences. 

Science reporter and BoingBoing podcaster Rose Evelyth put together this animated explainer a few years ago: 

What makes this so difficult to pin down, says Jim Lackner, a professor of physiology at Brandeis University, who has run research studies for the Navy and Nasa, is that it’s really hard to parse out any single cause or combination.

“There are a lot of interesting ways to think about it and a lot of ways to theorize about it, but it’s hard to integrate it all together,” said Lackner. “There is no single causative factor.”

Think about all the differing movements and stimuli in an external environment, explains Lackner, then think about all the internal variations, and add to that the ways a person’s brain and inner ear then adjusts to what’s going on.

“People differ greatly in having been exposed to a provocative stimulus, in terms of how quickly they recover,” he said. “Some people recover rapidly and other people may take a hundred times as long.  And we don’t know why.”

He and other scientists have been trying to better understand this, studying motion sickness outside on ships and inside in virtual reality labs. FMRI machines have been involved. NASA even researched this on what has come to be known as the “vomit comet,” or planes that can create near weightless environments.

“We move all the time and we don’t feel sick. The $64,000 question is what causes it?” said Tom Stoffregen, a professor of kinesiology at the University of Minnesota who is also trying to better understand motion sickness. “Why would a conflict between what you expect and what you experience make you feel nauseous? Nobody really has the slightest idea why the symptoms are what they are.”

Stoffregen doesn’t buy the widely accepted sensory conflict theory. He’s in the minority, but he thinks the main factor has to do with the stability of a person’s posture. He’s interested in the differences in the subtle ways our bodies sway when we’re still and in control, verses when we’re thrown around on a bumpy bus or a rocking ship.

He thinks that on board, the body loses its ability to maintain its natural posture and then struggles to compensate.

“You get on a ship, a ship moves around in ways you cannot predict,” he said. “You’re walking around, doing whatever you’re doing, so your foot is going to hit on the deck in ways you didn’t expect.”

But again, why that leads to barfing still stumps him.

Some have theorized that it comes from an evolutionary response, in which one’s inner ear system is triggered in the same way that it is when the body ingests a poison. 

What to do

Scientists think a more nuanced understanding of motion sickness could lead to better interventions and medications. But either way, if all of this is starting to make you feel dizzy, Stoffregen and others do agree there are some things people can do to avoid getting sick.

First, get behind the wheel.

“The best way to prevent getting carsick is to drive. No, seriously,” he said.

The driver doesn’t get sick. Same goes for pilots.

Stoffregen thinks that’s because the driver is in control. He or she can anticipate what’s coming, and more easily stabilize the body.

Dr. Hain, who follows the conventional sensory conflict theory, views it this way: when a person is focused on driving, the senses match up.

“When you’re looking outside, then the eyes are looking at a reference point. So as the car moves up and down, the ear is telling you the car is moving up and down,” Hain said. “And the eye is telling you you’re moving up and down.”

But this advice really won’t help if you’re a passenger on a bus, or if you’re two, like Aine, and can’t drive.

“Being in the front seat is better than back, and the big thing that anyone can do is keep your gaze outside the car,” said Stoffregen.

Focus on objects that are far away.

Stoffregen also points to a centuries-old technique used on ships.

“For thousands of years, mariners have said to novice passengers if worried about feeling sick go up on the deck and look at the horizon,” he said.

But whatever you do, he and others say, don’t read or look at electronics.

All of this is encouraging advice for Aine’s mom, who has an anti-puke plan for their next trip.

“We probably play a lot more ‘I spy’ with Aine to get her focused,” Mazer said. “And she’s not doing screens anymore in the back seat, which, as anyone knows, traveling with kids for five hours is probably a curse for all of us.”

As additional backup, Mazer also has a car seat that’s, well, easily washable.

And this update: Mazer and her family have since returned from their trip. While there were lots of false alarms, no one puked.