Nausea and vomiting are common symptoms of many illnesses and frequent side effects of cancer chemotherapy and radiation treatment. People with cancer and their caregivers can take several steps to prevent or relieve nausea and vomiting, ranging from diet changes to antiemetic drugs.

Causes of Nausea and Vomiting

Nausea refers to feeling queasy or having the urge to vomit, whether vomiting actually occurs or not. Nausea may be accompanied by increased salivation, sweating, dizziness, increased heart rate, loss of appetite and a general feeling of malaise. Retching, or “dry heaves,” refers to contractions of the stomach and esophagus that do not result in vomiting. Vomiting usually accompanies nausea, but it can also occur on its own.

The process that leads to nausea and vomiting is not straightforward. Nausea is largely controlled by an area of the brainstem referred to as the vomiting center. It is part of the autonomic nervous system that controls involuntary body functions such as breathing and digestion. This area is stimulated by nerves in the esophagus, stomach and intestines when they become irritated. Signals from the inner ear can trigger motion-induced nausea, and emotional states can also lead to nausea.

Vomiting is a reflex that involves contraction of the abdominal muscles and reverse peristalsis, or a reversal of the smooth muscle contractions that normally move food through the esophagus, stomach and intestines.

In addition to killing cancer cells, chemotherapy and radiation therapy can also kill off fast-growing cells elsewhere in the body including the intestinal lining, which can contribute to irritation. Some chemotherapy drugs trigger cells in the gut to release serotonin, a chemical messenger that stimulates the vomiting center.

Cancer itself can cause nausea and vomiting, especially if it has spread to the brain. Anesthesia given for surgery can also trigger nausea and vomiting. People who have low white blood cell counts as a side effect of radiation or chemotherapy may be more susceptible to food-borne infections, or food poisoning. Sometimes anxiety prior to undergoing treatment, in anticipation of side effects, can lead to a feeling of nausea.

The severity of nausea and how long it lasts varies from person to person. Some people have severe nausea during cancer treatment, while others taking the same drugs have little or no nausea. Some chemotherapy drugs are more likely to cause nausea than others, and higher doses typically lead to worse side effects. Nausea may be acute, occurring within minutes to hours after a chemotherapy session, but some people experience delayed nausea more than a day later or chronic (ongoing) nausea.

Managing Nausea and Vomiting

Changing what you eat and drink can help lessen nausea and make it easier to keep food down. The following tips may be helpful: 

  • Try eating small meals or snacks instead of three large meals.
  • If nausea occurs on an empty stomach, eat small snacks every few hours.
  • Sip clear fluids to stay hydrated, such as ginger ale, herbal tea, juice or broth.
  • Try foods that are bland and easy to digest, such as hot cereals or white rice.
  • Try eating dry, salty foods, such as saltine crackers or unbuttered toast.
  • Avoid fried, fatty, spicy and very sweet foods.
  • Avoid strong food odors.
  • Peppermint, chamomile and ginger can help relieve nausea.
  • Medical cannabis (marijuana) can help relieve nausea and restore appetite.
  • After eating, rest sitting up instead of lying down for at least an hour.

Find ways to relax the muscles involved in nausea and vomiting. Some people find relief from deep breathing, guided imagery, hypnosis, meditation or biofeedback. This can be especially helpful for anticipatory nausea prior to chemotherapy. Acupressure or acupuncture works for some people, including bands that stimulate a specific point on the wrist.

A variety of anti-nausea medications, known as antiemetics, can help prevent nausea or relieve symptoms. These range from over-the-counter products available at local drugstores to stronger medications prescribed by a doctor. Some of these drugs work by blocking the effects of serotonin or other neurotransmitters on the vomiting center. Ask your cancer care team about which ones to try.

Taking steps to prevent nausea may work better than trying to stop it. Keep a diary of when nausea and vomiting happen, their timing in relation to treatment and whether they are triggered by certain foods or situations. This can help inform a strategy to reduce nausea. Some antiemetic medications can be taken prophylactically before chemotherapy, or on a continuous basis through a pump, to keep nausea from developing.

Vomiting can cause dehydration and imbalances in body chemistry; it can also make it difficult to take oral medications. Prolonged nausea and vomiting can lead to weight loss and inadequate nutrition. Sports drinks can help replace lost minerals (electrolytes) and bananas are a good source of potassium. When you’re able to eat, choose foods that are high in nutrients and calories. Nutritional supplements may also be helpful. Talk to your care team if nausea and vomiting are prolonged (lasting more than a day) or continuous and you are unable to keep food down.

For more information on managing nausea, visit:

American Cancer Society
National Cancer Institute

Last Reviewed: November 20, 2017