Definition Motion sickness is the body's response to conflicting messages about motion that are sent to the brain. The conflict is between what the eyes see and what the body senses.
What is going on in the body? Information about motion and how the body is moving is obtained through the eyes and two places within the inner ear. This information is then sent to the brain so that the body can respond by coordinating muscles and maintaining balance. Information from these parts may indicate that a person is walking, doing hand stands, or even cartwheels. Other information is about the surface under a person or the area surrounding them. For instance, a person on top of a surfboard may not be moving but the surfboard and the water under the person is moving. Signals about the movement of the water and the surfboard are sent to the brain. These signals give information that helps the person to balance on the surfboard. When the brain receives one message from the eyes and another message from the inner ears, a person may feel the symptoms of motion sickness.
Different factors, such as speed, may cause motion sickness. Slow movement up and down while accelerating forward is more likely to stimulate motion sickness rather than fast movement up and down. For instance, more people feel motion sickness while riding a camel than riding a horse. Motion sickness is often reported while travelling aboard ships, but not while windsurfing.
Conflicting information regarding motion can be seen when a person is travelling on a ship looking out at the waves in the ocean. The inner ear perceives the up and down motion of the body riding on the ship, while the eyes perceive the random forward movement of the waves.
Another type of conflicting message occurs when the inner ear perceives movement while the eyes detect no movement. This can occur while standing or sitting still inside a moving ship or vehicle with no windows to visually explain the movement. It can also happen when a person is trying to read when travelling in a car. The inner ear perceives the movement of the car but the eyes detect no movement.
What are the signs and symptoms of the condition? Motion sickness is a normal response to an abnormal situation. It indicates that the feedback system of the eyes, inner ear, and the brain is healthy. The most common symptoms of motion sickness are nausea and vomiting. A person may also turn pale in colour, and break out into a cold sweat. An increase in oral secretions, yawning, fast breathing, headache, and drowsiness may also occur. Motion sickness, like that experienced on a ship, usually ends within 3 days of travelling. Some people adapt faster and may only experience symptoms for the first day or so.
What are the causes and risks of the condition? While there are usually no real risks associated with motion sickness, prolonged nausea and vomiting without eating or drinking can lead to dehydration and weakness. In this weakened condition a person may injure himself or herself due to a fall or accident.
What can be done to prevent the condition? Any person with a healthy inner ear system is susceptible to motion sickness. Some things make a person more susceptible and less able to adapt. This is likely due to the maturity or decline in function of the inner ear system. For instance, children between the ages of 4 and 10 are more susceptible to motion sickness. In contrast, elderly people tend to be more resistant to motion sickness. Women of any age, but especially during menstruation or pregnancy seem to be more vulnerable as well.
Measures to reduce or prevent motion sickness include:
eating a small light meal no less than 3 hours before exposure
focusing on a stable horizon or distant focal point while in motion
limiting head movements
staying centrally located while travelling on a boat or plane
sitting up front or driving when travelling in a motor vehicle
avoiding reading or needlework when travelling in a motor vehicle
staying in a well ventilated area
How is the condition diagnosed? There is not a test to diagnose motion sickness. It is usually diagnosed after a person has had motion sickness and asked his or her doctor for help. The doctor may discuss past episodes of motion sickness with the person in order to find ways to prevent it in the future.
What are the long-term effects of the condition? The lingering effects of motion sickness will depend on how long a person is exposed to the stimulus and how severe the symptoms are. Once the stimulus causing motion sickness is removed, the actual symptoms will usually stop within a few minutes to a couple of hours. No long-term effects can be expected.
What are the risks to others? Motion sickness is not contagious.
What are the treatments for the condition? Treating motion sickness focuses on easing any nausea and vomiting. These symptoms usually are caused by chemicals that are released in the body and stimulate the vomiting centre in the brain. The goal of medication is to block the effects of these chemicals on the brain. Prescription medications are available in the form of a patch worn behind the ear. This patch is not recommended for children. There are also over-the-counter drugs that do not require a prescription. These medications are antihistamines, such as diphenhydramine. The most common home remedy for motion sickness is ginger, although there is no scientific evidence that it is effective.
What are the side effects of the treatments? The most common side effects of both the patch and over-the-counter antihistamines is dry mouth, blurry vision, and drowsiness. A doctor may prescribe other medications that can offset these side effects.
What happens after treatment for the condition? Rest and relaxation is encouraged after treatment.
How is the condition monitored? Monitoring of the person experiencing motion sickness is only necessary to provide appropriate comfort and safety measures. These may include medication, fresh air, fluids, and small meals. Motion sickness is different for every person. The intensity of symptoms depends upon the person, along with the amount of time and the source of stimulus causing the motion sickness.
Author: Linda Agnello, RN, BSN Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
