(CNN) — Travel sickness isn’t just hearsay. Nearly a third of people experience motion sickness – and to this day we don’t exactly know what causes it. The prevailing theory suggests it is triggered by a poor perception of movement.

Departure to and return from summer vacations seem moments especially prone to the stealthy advances of this sickness. We (or at least those of us inclined to travel sickness) are more often ill during these particular journeys than during our normal comings and goings.