Quoted from Wikipedia, for what it's worth.

Nausea

Ginger has been found effective in multiple studies for treating nausea caused by seasickness, morning sickness and chemotherapy,[10] though ginger was not found superior over a placebo for pre-emptively treating post-operative nausea. Ginger is a safe remedy for nausea relief during pregnancy.[11] Ginger as a remedy for motion sickness is still a debated issue. The television program Mythbusters performed an experiment using one of their staff who suffered from severe motion sickness. The staff member was placed in a moving device which, without treatment, produced severe nausea. Multiple treatments were administered. None, with the exception of the ginger and the two most common drugs, were successful. The staff member preferred the ginger due to lack of side effects. Several studies over the last 20 years were inconclusive with some studies in favor of the herb and some not.[12][13] A common thread in these studies is the lack of sufficient participants to yield statistical proof. Another issue is the lack of a known chemical pathway for the supposed relief.