Chemotherapy and radiation therapy are the most common causes of nausea and vomiting in patients being treated for cancer.

Nausea is controlled by a part of the central nervous system that controls involuntary body functions (like the heart beating). Vomiting is a reflex controlled by a vomiting center in the brain. Vomiting can be triggered by smell, taste, anxiety, pain, motion, poor blood flow, irritation, or changes in the body caused by inflammation.

The most common causes of nausea and vomiting are:

• Chemotherapy.
• Radiation therapy to the gastrointestinal (GI) tract, liver, or brain.

Many factors increase the risk for nausea and vomiting.

Nausea and vomiting are more likely if the patient:

• Had severe or frequent periods of nausea and vomiting after past chemotherapy sessions.
• Is female.
• Is younger than 50 years.
• Has a fluid and/or electrolyte imbalance (dehydration, too much calcium in the blood, or too much fluid in the body's tissues).
• Has a tumor in the GI tract, liver, or brain.
• Has constipation.
• Is receiving certain drugs, such as opioids (pain medicine).
• Has an infection or blood poisoning.
• Has kidney disease.
• Has anxiety.