Nausea and vomiting are some of the most dreaded side effects of chemotherapy. Some chemotherapy drugs are more likely than others to cause this symptom, but options are available for even the most nausea-inducing drugs. Fortunately, options for both treating and preventing nausea have advanced so that many people now experience little or no nausea.
Nausea refers to the stomach upset that may or may not precede vomiting, and is a very common side effect of chemotherapy medications. Chemotherapy works by attacking any rapidly growing cells in the body, and just as cancer cells divide rapidly, so do those in the hair follicles (causing hair loss), bone marrow (causing anemia and low white blood cell counts), and digestive tract (causing nausea).
Some chemotherapy medications are more likely to cause nausea than others, and everyone is different when it comes to the amount of nausea they will experience. While the treatment of chemotherapy-induced nausea has come far in the last decades, it's estimated that at least 70 percent of people still experience some degree of nausea during and after chemotherapy.
Chemotherapy can lead to nausea and vomiting in several ways. The most common cause is activation of areas in the nervous system that control vomiting. This was initially challenging to treat as the drugs essentially told the brain that they were nauseous. Sometimes chemotherapy medications alone or in combination with other medications can irritate the stomach lining.
Ginger and Nausea Reduction
It's not known exactly how ginger works in the body to reduce nausea. Ginger contains oleoresins, substances that have an effect on the muscles of the digestive system. Ginger also has anti-inflammatory effects in the body. 
A 2012 study to evaluate the best dose of ginger also found a significant reduction in nausea among people who used ginger. In this study, patients were given a placebo or 0.5 grams, 1 gram, or 1.5 grams of ginger divided twice a day for 6 days, and beginning 3 days prior to the chemotherapy infusion. The most effective dose in this study was 0.5 to 1.0 grams.3
Chemotherapy can cause nausea immediately, or over several hours and days following infusion. Another 2012 study done with breast cancer patients found that ginger was most effective in alleviating nausea that occurred between 6 and 24 hours following chemotherapy.4 Yet another study performed on children and young adults with cancer found that ginger helped with both acute (within 24 hours) and delayed (after 24 hours) nausea associated with chemotherapy.
While ginger appears to help with nausea, a 2015 study found that ginger helped with nausea and episodes of vomiting, but did not decrease the episodes of retching experienced by women with breast cancer.5
Results of a 2017 study published in the Annals of Oncology suggest that the effect of ginger on chemotherapy induced nausea and vomiting may vary between men and women, by cancer type, and by drug, making previous studies somewhat difficult to interpret.
Studies   done to evaluate how ginger may reduce nausea suggest that it is the rhizome that holds the active ingredients. Both gingeral and shogaol compounds appear to affect gastrointestinal motility and gastric emptying rate but also affect neurotransmitters in the brain that may affect nausea.7
 Treatment of Chemotherapy-Induced Nausea in Cancer Patients. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3188425/
 Efficacy of Ginger in Ameliorating Acute and Delayed Chemotherapy-Induced Nausea and Vomiting Among Patients With Lung Cancer Receiving Cisplatin-Based Regimens: A Randomized Controlled Trial. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6142108/
 Ginger (Zingiber officinale) reduces acute chemotherapy-induced nausea: A URCC CCOP study of 576 patients https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3361530/
 The Effectiveness of Ginger in the Prevention of Nausea and Vomiting during Pregnancy and Chemotherapy https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4818021/
 Ginger as a miracle against chemotherapy-induced vomiting. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3703071/