An area of the brain called the vomiting centre controls nausea and vomiting. Nausea or vomiting happens when the vomiting centre is stimulated. It may be stimulated by:
- nerves in the gut (stomach)
- another part of the brain called the chemoreceptor trigger zone (CTZ)
- the inner ear, which is caused by body motion
- our senses – for example, taste, smell and pain
- our emotions – for example, if we are scared or nervous.
There are several reasons why someone with cancer may have nausea and vomiting. These include cancer treatments, physical changes in the body and emotional reasons. Some of the reasons why someone with cancer may experience nausea and vomiting are listed below.
Treatments that can cause nausea and vomiting
Cancer treatments that may cause nausea and vomiting include:
- radiotherapy, if given to the brain, stomach, bowel or close to the liver
- hormonal therapies
- targeted therapies
- morphine-based medicines, which are used as painkillers.
Physical causes of nausea and vomiting
Sometimes, nausea and vomiting can be caused by the following reasons:
- Changes in the body chemistry. High levels of calcium in the blood can cause nausea and vomiting.
- Pressure in the brain. If the pressure in the brain is raised, it can affect the vomiting centre and cause you to be sick.
- Damage to the liver. If the liver is not working properly, waste products can build up in the blood, leading to nausea and vomiting.
- Constipation. This can sometimes cause nausea and vomiting.
- Bowel obstruction. Some cancers, especially cancers that affect the pelvis or abdomen, can cause the bowel to become blocked (bowel obstruction), making you vomit.
Emotional causes of nausea and vomiting
In other cases, there are emotional reasons for nausea and vomiting, such as the following:
- Anxiety. Feeling anxious about the cancer or your treatment may cause nausea and vomiting.
- Feelings of nausea and vomiting before treatment (anticipatory nausea). Sometimes, feelings of nausea and vomiting can be triggered by a situation that reminds you of when you were feeling or being sick in the past. This is called anticipatory nausea. It can occur with chemotherapy and other cancer treatments.