Why do people get car sick?

In response to this article:

I found that the original question wasn’t answered. The article does say what triggers motion sickness but not why it occurs. Clearly your body is deciding to empty your stomach when getting conflicting information, but what’s the point? I understand that nausea due to actual sickness or poison (including alcohol) is an attempt to remove a harmful substance from your system, and that makes sense. But this seems pretty random to me. Is your body just trying to get your attention? Is it throwing a tantrum because the brain is pissing it off? I’m afraid I just don’t get it…

Disorientation/vertigo is a common symptom of poisoning, so when you feel disoriented or vertiginous, your brain interprets it as meaning that you might have been poisoned.

Doesn’t explain the awful feeling in your head, though. Nausea by itself is not nearly so bad.

I can get motion sickness with my eyes closed – it’s clearly not just eyes and ears. And there are some reasonable effective ent90emetics now as well (that don’t make you go blind).

And there is clearly a psychosomatic element as well.

Oh that’s interesting. I got it so bad as a kid which was terrible on family vacations. Around when I turned 18 I completely ceased to get it. My wife still gets it bad and she is 50.

Thanks for the answer Chronos, that makes sense. :slight_smile:

The column does say that the ears have two components, static and dynamic equilibrium. So it’s not merely eyes vs ears, but rather eyes vs ears vs ears. In some people, any two in disagreement could cause discomfort.

I’m not sure I buy that. There doesn’t need to be an evolutionary answer to everything. Disorientation and nonequilibrium are just things that make us want to puke.

The truth is that we don’t really know “why”.

What we do know is that when you stand on your two feet, you remain upright through a combination of your vestibular organ (sitting in the skull, behind your ear), your vision (your eyes) and stretch receptors in the tendons of some of your muscles (e.g. your Achiles’ tendons: as you lean forward with your feet on the ground, tension increases in the tendons).

What we also know is that your vestibular organ contains “hair cells”, that is cells with little, < 1-micron “hairs” that measure the movement of fluid in the vestibular organ, for instance in response to your body turning. These cells are very active; as a matter of fact they have the highest metabolic rate of any cell in the body.

What most people in the field believe is that: since these cells are very fragile and use a lot of energy, any poison in the body will first affect them. Thus, if there is a discrepancy between the left and right vestibular systems, or between your sense of vision and your sense of balance, you might have just ingested a poison.

Therefore if you are in a car, looking down and reading, your sense of vision tells you things (for instance the book you are reading) are not moving, whereas your vestibular sense tells you otherwise (it senses the car is turning). The discrepancy is interpreted in some people’s bodies as “we might just have ingested a poison, let’s chuck it out”.

This also account for the fact that most people experience “VR sickness”, i.e. motion sickness when stationary but being immersed in a “Virtual Reality” environment.