Motion sickness (or seasickness) is a general sense of not feeling well (malaise), nausea, vomiting, headache, and sweating that occur with movement. It develops when the inner ear, the eyes, and other areas of the body that detect motion send conflicting messages to the brain.

Motion sickness occurs when one part of the balance-sensing system (inner ear, joints and muscles, or vision) may indicate that the body is moving, while the other parts do not sense motion. For example, when a person is in the cabin of a moving ship, the inner ear may sense the motion of big waves, but the eyes don't see any movement. This leads to a conflict between the senses and results in motion sickness.

Motion sickness is usually just a minor sense of queasiness and does not feel like a serious medical illness. However, some travelers are quite sick with it, and a few even suffer symptoms for a few days after their trip. Once motion sickness has developed, treatment consists of stopping the motion. If the motion cannot be stopped, sitting or lying down in an area that appears to move the least may help. In an airplane, sitting over the wings may feel more stable; on a boat or ship, staying on the deck, looking at the horizon, or sitting or lying down in a cabin near the center of the ship may help.

Prescription and nonprescription medications may prevent and treat symptoms. Some people find that taking ginger or wearing acupressure wristbands can help reduce symptoms of motion sickness.