Motion sickness

Motion sickness is a syndrome marked mostly by nausea or vomiting because of the conflict inside the patient's mind regarding the true vertical axis and the perceived vertical axis. It is most common between ages 2 and 12 and can be felt anywhere from boats to rocket ships to cinemas.
Treatment options include diazepam and diphenhydramine, but many sufferers have found relief by just eating small quantities of food once they begin to feel ill.
Motion sickness at Wikipedia