Motion Sickness and Human Performance Laboratory, Israel Naval Hyperbaric Institute, Haifa.
Salivary composition and flow rate were measured in 13 healthy male volunteers exposed to a real seasickness situation. The flow rates of whole unstimulated and stimulated saliva were significantly reduced at sea in about 80% of the subjects. Salivary flow rate was negatively correlated with seasickness severity. These results contrast with the classic concept of increased salivation during seasickness. At sea, the potassium concentration of both unstimulated and stimulated saliva was significantly reduced, while sodium concentration was consistently elevated. The sodium and protein concentrations were positively correlated with seasickness severity. Thus, objective measurements of salivary flow rate and composition may be recommended for evaluation of the seasickness syndrome.