What is Seasickness: An Introduction

Sailing is a pleasant thing, or at least, it normally is as long as you can avoid spending most of you time on board throwing up. Seasickness is a common reaction to long stays offshore, and has the potential to spoil the most memorable cruise. This article should give an introduction to the causes of seasickness – and how to treat it.

Seasickness, sometimes called “mal de mer” which means the same but comes with French chic, affects mostly people who are not used to spending much time on a boat. It is more common under rough weather conditions. It is based on a conflict of sensory input, that our brains can’t handle.

If you stand on solid ground, a sensory organ in your inner ear uses the stream of liquid around very fine hair to feel the position and movement of your body with respect to your environment. It works similar to a gyrometer – if you move left, the momentum of the liquid in your balance sense organ resists the motion. The fine hair, however, does move instantly since it is physically attached to your body and bends in the liquid. This behavior is felt and the organ sends a signal to the brain.

There, the brain receives information not only from the sense of balance, but from all kinds of sense organs. Humans are very visual and from our early childhood on, we trust optical signals more than any other sensory input. If we move and the brain receives the “the hair in the inner ear says: you are turning left!”, it tries to match this with visual input. If you stand on solid grounds, your eyes will confirm your motion with respect to your surroundings.

So much more than just a drawback of your sailing vacation...

But how does this work on a moving sailing vessel? There your brain receives the signal: “the hair in the inner ear says: you are turning left – and down; no, wait, up in fact and slightly to the right – and back again!”. But if the brain tries to match this information with what your eyes see, it gets confused: since it is the entire ship that moves with you, the eyes fail to perceive the motion with the same intensity as your sense of balance does. The brain is confused and solves the conflict with a simple reaction: Throw up!

The idea is that vomit always falls down and that this way, your eyes will be able to tell where you are going. Well, not really. The brain is just confused, you start to feel sick and then you can call it “seasickness”, even though the same issue applies in any situation with the described circumstances. Be it in a car, a bus or a plane – some people get sick in trains. The cause is always the same dilemma: conflicting information about your movement from different sources.

So this is seasickness. It might start with a funny tummy, but at latest when you start vomiting, it becomes a serious issue and should be treated with much consideration. Throwing up means that you deprive your body from water supply, and dehydration leads to headaches, dizziness and a loss of orientation. If the seasickness itself didn't already do the job.

People who are seasick don’t make good sailors, so do take care to put effected ones to rest. In most cases, the brain adjusts within hours or days to the new situation and learns to ignore the sickening senses.

Read in “How to beat Seasickness” what you can do against it!

What is Seasickness: An Introduction

So much more than just a drawback of your sailing vacation...

Further Reading