If you get sick riding in a car or on a boat (or a roller coaster), you take Dramamine, right? It’s a pretty well known remedy. But Dramamine is an antihistamine. Have you ever wondered what an antihistamine has to do with motion sickness?
Histamine and Motion Sickness
Histamine does more than just trigger allergic responses. In the hypothalamus of the brain, a histamine-triggered system receives input via the vestibular (where your body is in space), visual, and sensory input (somatosensory) systems. When there’s a conflict between these (because, say, the body is in motion, but the eyes can’t see where it’s going), this triggers histamine release. The histamine then lands on the H1 receptors in the brainstem which control the vomit (emetic) response. (The mismatch trigger is the reason why most people with motion sickness feel better when they can see where they’re going, by the way: so sitting in the front seat rather than the back seat of a car for instance.)
Dramamine (and similar medications) affect histamine’s H1 receptors in the brain, blocking this stimulus.
So then the question becomes—are those with elevated histamine levels more at risk for motion sickness?
Who Has High Histamine?
I wrote here on histamine intolerance, a condition of elevated histamine levels in the bloodstream, generally secondary to gut inflammation.
Mast Cell Activation Syndrome involves many of the same symptoms, but has a different cause: the cells that carry histamine (mast cells) are generally overreactive, causing constant release of their contents—including histamine.
Both of these patients will have higher circulating levels of histamine than the average person. But does that make them more susceptible to motion sickness than others?
While I haven’t found any studies that specifically answer this question (most say we still don’t know why some people get motion sick and others don’t), this study implies that high histamine might increase susceptibility: Vitamin C has been shown to reduce motion sickness substantially by reducing histamine levels (as Vitamin C is a mast cell stabilizer).
If you tend to get motion sickness, consider loading up on Vitamin C before your next excursion… and you might also consider checking your whole blood histamine levels. It just might be a clue to something else going on in your body.