Motion sickness is caused by a conflict between what your eyes and other senses tell your brain.
Your eyes adjust to motion but the inner ear, which contains fluid-filled canals that control balance, does not. The resulting signals to the brain from the eye and the inner ear do not tally and the brain becomes confused, which can leave you with a horrible feeling of nausea, dizziness and an upset stomach.
Not eating a large meal before or during travel can help, but equally it is important not to travel on an empty stomach. When you don’t eat, the stomach becomes very unstable, making it easier for you to feel sick.
Do drink plenty of fluids so as not to become dehydrated but avoid fizzy drinks as these are likely to cause or worsen an already upset stomach.
Don’t read! As your eyes focus on the page rather than the motion of the vehicle you’re in, your brain is likely to feel disorientated.
Finally, taking ginger before you travel may also help. A plant native to South East Asia where it is used extensively in cooking, ginger can also help with nausea and sickness.