Why Do Some People Get Motion Sick And Others Don't?

For thousands of years, humans have been getting queasy on boats. People have long felt a rumbling in their stomachs and then braced themselves against the side of the ship in hopes the feeling might pass.

Hippocrates wrote about motion sickness more than 2,000 years ago, and the word “nausea” stems from the Greek word naus, meaning “ship.”

Scientists now understand what causes motion sickness and how it can be prevented. And studies find it’s something almost everyone will have to endure at one point in their life.

Scientists currently explain motion sickness through the sensory conflict and neural mismatch hypothesis, which they first proposed in the 1970s. The sensory conflict hypothesis is the most widely accepted explanation as to why people can feel sick to their stomachs while traveling in boats, cars, or planes.

It’s also being used to explain why some virtual reality experiences can leave players feeling vomitous. (Although the theory is accepted, experts sometimes debate the name.)

Read More: The Controversial Condition of Sensory Processing Disorder

The sensory conflict hypothesis holds motion sickness results when there is a conflict between what a person’s inner ear detects and what their eyes visually process. On a rocky ship or a turbulent plane, the inner ear senses movement. The person’s field of vision, however, may appear stable.

A person in the backseat of a car, for example, might feel the turns the car is making. But the headrest they are staring at in front of them doesn’t move. The result is a “perceptual incongruity” between the inner ear and visual processing.

In response, the brain produces stress-related hormones, which can cause a person to feel dizzy or nauseous. One journal described the symptoms as involving “stomach awareness,” which may be a pleasant way of saying nausea and vomiting. Other symptoms involve turning pale, sweating, and salivating. 

Read More: The Biology of Stress in Your Body

Almost everyone will experience motion sickness at some point in their life. However, studies have found that some people are more susceptible.

In a 2020 study in Transportation Research, researchers had more than 4,400 people in Brazil, China, Germany, the U.K., and the U.S. take an online survey regarding their travel behaviors and motion sickness.

The researchers defined motion sickness as the feeling of illness that stems from any type of travel (including roller coasters) and results in a range of symptoms, including fatigue, dizziness, and vomiting.

The time for motion sickness symptoms to appear varies based on the trigger. Activities like reading and exhaust or cigarette smells typically induce symptoms in about 10 minutes, while motion sickness from driving dynamics has a slightly longer onset time, with a median of 15 minutes.

Here's what researchers from the study identified as the most common reasons for getting motion sickness:

• Age and Gender

Younger individuals and females are more prone to motion sickness compared to older people and males.

• Role in Transportation

Drivers are less likely to experience motion sickness than passengers.

• Screen Usage

People who focus on screens, like smartphones, are more likely to report feeling motion sickness.

• Common Scenario

Motion sickness is frequently reported on boats (62 percent), in the back seat of a car (46 percent), on buses (40 percent), and occasionally on airplanes (about 33 percent). It's less common on subways (less than one-third).

• Triggers

Participants identified several triggers for motion sickness, including roads with frequent turns (72 percent), cigarette or exhaust smells (71 percent), and curvy roads (70.5 percent).

• Stop-and-Go Traffic

Approximately 57 percent of individuals attributed their motion sickness to stop-and-go traffic conditions.

• Personal Activities

More than half of participants admitted that their own activities contributed to their motion sickness. This includes reading (67 percent), writing (59.4 percent), device usage (61.7 percent), and video watching (58 percent).

Read More: The Science of Migraines

The most effective method to prevent motion sickness is by avoiding situations that create perceptual incongruity. It's advisable for travelers to refrain from reading in a car or indulging in cat videos on a bus. Instead, focus on the horizon or gaze out the window, allowing your senses to align and reduce the conflict between your ears and eyes.

• Over-the-Counter Medications

For individuals prone to motion sickness, over-the-counter anti-nausea medications like diphenhydramine (Benadryl) or dimenhydrinate (Dramamine) offer a solution to prevent that woozy feeling. Typically, these medications should be taken an hour before embarking on your journey. Remember to stay well-hydrated, as these medications can have a dehydrating effect, so it's a good idea to pack water.

• The Handy Barf Bag

To alleviate any anxiety related to motion sickness, it's wise for travelers to carry a convenient barf bag. Having one readily available can provide peace of mind in case of nausea.

• Odor Awareness

Travelers should also be mindful of specific odors that can exacerbate the feeling of sickness. On boats, for example, strong odors like pungent fish or diesel fumes can intensify queasiness. It's best to avoid standing near the motor to reduce your body's reaction.

• Seek Solid Ground

For some individuals, the only way to find relief from motion sickness is to disembark from the boat or plane. Fortunately, in most cases, motion sickness tends to resolve within 12 to 24 hours.

Read More: What Is Tinnitus: It's Causes, Effects and Brain Connections