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What is motion sickness?
Motion sickness describes the feelings of dizziness, sickness and nausea that occur when you're travelling in a moving vehicle, such as a car, boat, aeroplane or train. You may also experience motion sickness from riding on an amusement park ride, playing video games, or watching a 3-D movie. The condition is also sometimes known as travel sickness, car sickness, sea sickness or air sickness.
During motion sickness, balance sensors in the inner ear send signals to the brain that do not match what your eyes are processing. For example, your eyes may see the landscape passing by at high speed, while your balance structures are sensing that you are sitting still. This confusing information is felt as motion sickness.
Although anyone can get motion sickness, it is most common in children between about two and 12 years of age. Women also tend to be more commonly affected than men, while infants and toddlers are usually resistant.
The brain receives signals about motion and balance from three main areas: the eyes, inner ears and muscles. Motion sickness occurs when unusual movements send conflicting signals to your brain. For example, some unusual movements that may occur during car travel could include winding through the mountains, passing over a bumpy surface or driving in circles.
Of the three areas that are responsible for sensing motion, the structures of the inner ear are thought to be the most important. The inner ear contains three fluid-filled tubes arranged at different angles, known as the semicircular canals.
As the head moves, fluid flows through the semicircular canals, sending information to the brain about the speed, direction and distance of the movement. Together, these structures in the inner ear make up the body's balance centre, known as the vestibular system.
If you are sitting still during a journey, information on this lack of movement is sent to the brain by your inner ear and muscles. In contrast, your eyes are signalling that you're travelling at speed. These mixed messages trigger the symptoms of motion sickness.
In some cases, motion sickness may also develop from playing video games, watching a 3-D movie, or any other activities that also send misleading signals to your brain.
Some factors that may increase your chances of developing motion sickness include:
- Age - being a child aged between about 2-12 years old;
- Sex - being a woman, particularly during pregnancy or menstruation;
- Poor ventilation, particularly when there are also strong fumes or food smells;
- High levels of stress, fear or anxiety;
- Being prone to migraines, and;
- Taking medications that increase nausea, such as certain contraceptives, antidepressants, antibiotics or opiates.
Signs and symptoms
Common symptoms of motion sickness include:
- Fast, shallow breathing;
- Turning pale;
- Headache, and;
In most cases, these symptoms pass after motion has stopped. However, in a small number of cases, dizziness and nausea may continue after a journey has ended.
Methods for diagnosis
As motion sickness usually only develops under particular circumstances, many people visit their doctor for advice on preventing motion sickness, rather than while symptoms are occurring. For this reason, your doctor will usually make a diagnosis by asking about symptoms after the event.
Types of treatment
Some people may build up a tolerance to motion sickness over the course of a long journey or after repeated trips in a car, boat, aeroplane or train. Eventually, symptoms may not develop at all. Similarly, children who experience motion sickness frequently while they are young, may outgrow it during their teenage years. However, short-term treatment options include:
To relieve the symptoms of motion sickness, you may find it helpful to try one or more of the following options during travel:
- Focusing your vision on the horizon or a fixed point in the distance;
- Keeping head movements to a minimum;
- Avoiding looking at a map or reading;
- Opening a window or taking a break to get some fresh air;
- Distracting yourself with breathing activities, calming music or mental activities;
- Reclining your seat or lying down;
- Maintaining a comfortable body temperature, and;
- Avoiding heavy meals or alcohol.
The most well-known alternative therapies for motion sickness are acupressure wrist bands and ginger, often taken either as a biscuit, tea or supplement. These options may provide relief for some people, but research into their effectiveness has shown mixed results.
Motion sickness slows down digestion, which can prevent the body from absorbing medications effectively. For this reason, medications for motion sickness are usually taken before travel to prevent symptoms, rather than as a treatment. The options include:
Hyoscine is thought to prevent motion sickness by blocking some of the confusing signals sent from the inner ear to the brain. It is available in oral tablet form without a prescription. Side effects of taking hyoscine may include a dry mouth, dizziness, drowsiness and blurred vision. For these reasons, hyoscine is not a suitable treatment if you are planning to drive for part of a journey.
Although antihistamines are perhaps most widely known as a treatment for allergies, these medications may also help to prevent nausea and vomiting. Common antihistamines prescribed for motion sickness include promethazine and dimenhydrinate.
As these antihistamines cause drowsiness as a side effect, they are also sometimes referred to as 'sedating' antihistamines. In general, they tend to be less effective than hyoscine, but with fewer side effects.
In severe cases of motion sickness, extended bouts of vomiting can lead to dehydration and low blood pressure, particularly in children. However, it is uncommon for motion sickness to progress to this stage.
Although motion sickness may be unpleasant, it usually fades after the movement has stopped. There are also several ways to treat and prevent the condition, involving behavioural modifications, medications, or a combination of both.
To prevent motion sickness, you may find it useful to sit in the front seat or be the driver when travelling by car. Similarly, sitting on the upper deck of a boat, facing forward on a train or over the wing of a plane may limit the confusing signals sent to your brain. Eating and drinking as little as possible and avoiding alcohol or strong smells during travel is also recommended.
In some people, keeping the head still, lying down flat or keeping the eyes closed while moving, may prevent or reduce symptoms. Other activities that may help you to relax include listening to calming music, doing controlled breathing exercises or opening a window for fresh air and maintaining a comfortable body temperature.