Ginger is a plant believed to have originated in South Asia.
Extracts of ginger have been found to be effective antiemetics, and ginger is believed to have at least one (likely more than one) pharmacologically active compound which inhibits activation of 5-HT3 receptors. Lete and Allue (2016) noted that "6-shogaol, 6-gingerol, and zingerone could inhibit the 5-HT response in a concentration-dependent manner, with 6-shogaol exhibiting the greatest potency." This mechanism of action is analogous to pharmaceutical products that are approved by the FDA and other agencies for use as antiemetic agents, such as ondansetron (Zofran).
The primary constituent of ginger plants is 6-gingerol, which itself is believed to have antiemetic properties. However, the exact chemicals responsible for antiemetic activity have not been conclusively identified, and the health benefits of ginger may be derived from a number of active compounds, as is the case with kratom and cannabis.
As a 5-HT3 antagonist, it is possible that excessive use could result in Serotonin Syndrome, especially when paired with other drugs that affect serotonin, such as SRIs including SSRIs and SNRIs. However, the FDA has not documented this reaction to ginger. There are, nonetheless, anecdotal claims of this result.