Motion sickness occurs when the body is subjected to accelerations of movement in different directions or under conditions where visual contact with the actual outside horizon is lost. The balance center of the inner ear then sends information to the brain that conflicts with the visual clues of apparently standing still in the interior cabin of a ship, airplane or car. From one third to one half of airline passengers will experience some degree of motion sickness when encountering heavy turbulence. It has been found that fear or anxiety can lower the threshold for experiencing symptoms, however some individuals seem to be naturally prone to motion sickness since childhood. Symptoms generally consist of dizziness, fatigue, and nausea which may progress to vomiting. Prevention is best accomplished by seeking areas of lesser movement in an interior location of a large ship or by facing forward and looking outside a ship or plane. Several medications are now available both by prescription and over the counter that may prevent or limit the symptoms of motion sickness. If medications are necessary, they are best taken at least one hour before embarking. The OTC medications Dramamine or Bonine can be very effective for short trips or when symptoms occur intermittently. For longer trips, a prescription medication called Transderm-Scop comes in the form of a patch can be worn behind the ear for up to three days at a time. Side effects of these medications usually consist of sedation and dry mouth and they should not be taken by people who have glaucoma or urinary obstruction.