Bernard Wilkinson, of Oamaru, asks :-

Why do some people get seasick and others in the same boat don't? Are there any good cures for seasickness ?

John North, the Fleet Medical Officer in the Royal New Zealand Navy, responded.

Seasickness, which is a form of more generalised travel sickness, occurs due to a perceptual conflict between visual and vestibular information being processed by the brain. This causes a sensory mismatch, an eye/ear disconnect to which different individuals have different sensitivities and hence different tolerances and experiences.

Although inducible by anticipation and aggravation by certain odours, or reading etc. it is not uncommon. Up to 75% of sufferers develop some level of acclimatisation and hence tolerance to movement with time and exposure .

There does appear to be a genetic factor, in that some families tend to suffer more from seasickness than do others. Certain groups of people are more prone to seasickness than others, particularly; children, women (especially when pregnant and around menstruation), and migraine sufferers. Also those with certain inner ear conditions, after head injury, and those on some medications including the combined oral contraceptive

There are many non-pharmacological "cures" which are reported, reflecting the individual nature of responsiveness. Some are sworn to work by devotees and found to be ineffective by others. Common suggestions include; looking at the horizon, fresh air, lying down, wrist bands, an ear plug in the dominant ear, and ginger

Pharmacological approaches commonly include; sedating oral antihistamines, eg Cinnarizine, Cyclizine or Promethazine, and dermal patches containing Hyoscine.

Interestingly, the worst of storms, ie the biggest waves, aren't necessarily the issue. In that situation the ship is faced into the gale and just goes up and down which is not too bad. Slightly easier seas where the ship is still making way across the direction of the storm or, possibly obliquely, can be much worse as the ship makes a 'corkscrewing' motion. Up to half the ship's company may be significantly affected in such situations, a real challenge for the medic on board to manage and ensure that personnel can continue to perform their duties safely. I have no exact figures for this, just experience - mine and others.

Occasionally someone joins the sea-going navy only to find they never overcome seasickness but these are rare and it usually becomes apparent during training if it is a major issue. Others leave their careers earlier than they might perhaps do otherwise if they find it excessively unpleasant to be at sea.