How do travel sickness pills work?

You’re going on a trip. You’re so excited you think you’re going to vomit. No wait, it’s travel sickness again.

Whether you suffer from emetophobia or not, nausea and vomiting is never nice. Travel sickness can easily ruin that special trip to Disneyland, at any age. Tablets can seem like a miracle pill, but how do they actually work?


Travel sickness, or travel-associated motion sickness, is caused by confusing information sent to the brain from the senses, mainly the vestibular system and the eyes.

The vestibular system is found in the inner ear. It’s a complex of nerves, small channels and fluid that provides the brain with information about motion. It’s this system that means your brain knows how and where you’re moving, even with your eyes closed. It does this using the information about the changing position of the fluids.

Motion sickness comes about when there is conflicting information between the eyes and the vestibular system. For example if you’re reading in the car your eyes will be transmitting information that you are stationary, while your vestibular system will pick up the repetitive motion of the car. This clash of sensory information can result in dizziness, nausea and vomiting.

The condition is often more common in children between three and twelve, which is thought to be because their vestibular system hasn’t matured yet.


Tablets for travel sickness can be a particularly effective treatment. Medication works to block the signals from the vestibular system, and therefore dampen the information that conflicts with the other senses.

Hysosine, also known as scopolamine or Kwells tablets, acts directly on the vestibular system. The nerve signals to the area of the brain that controls vomiting are blocked. This is turn inhibits the signals to the stomach which cause nausea and vomiting. This method of prevention is particularly effective but its effects are relatively short-lived.

Promethazine, the active ingredient in Avomine, is an antihistamine. Antihistamines are most commonly used to combat allergies but promethazine also improves the blood flow to the inner ear. This means it can be used to block the clashing message from the vestibular system. Although it takes longer to work, it’s advised that they are taken one or two hours before your journey begins, the compound will also stay in your system for longer.

Always be aware that any medication can have side effects. Both treatments have been reported to have a sedative effect. Neither should be used when driving, or operating heavy machinery (if the opportunity crops up), unless you are certain they don’t affect your alertness. If you are driving consider how travel sickness medication may affect your awareness later on.

It’s important not to mix and match medications. Many treatments that are effective for nausea in other medical conditions aren’t effective for motion sickness. This is due to the fact that the vomiting centre in the brain has multiple trigger zones. Common nausea treatments, such as metoclopramide, block chemo-receptors rather than the vestibular system, which causes the symptoms of travel sickness.

Be aware that travel sickness medication treats the symptoms rather than the cause. As well as tablets, behavioural techniques, such as sitting in the front of vehicles and focussing on distant objects, may help to alleviate motion sickness.

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