Underlying causes of vomiting

10-minute read

Key facts

Vomiting is a symptom, not a disease or condition.
Vomiting can be classed as acute (a short term isolated attack) or chronic (ongoing or recurrent).
Gastroenteritis and food poisoning are the most common underlying causes of sudden vomiting and usually clear up without treatment in a couple of days.
Vomiting can sometimes be a symptom of something serious.
Recurrent vomiting or vomiting that has lasted more than 2 days should always be investigated by your doctor.

Vomiting is one of the symptoms of COVID-19. Even if your symptoms are mild, get tested for COVID-19 immediately — use the COVID-19 Symptom and Antiviral Eligibility Checker if you're not sure what to do.

What is vomiting?

Vomiting is a symptom, not a condition. It has many different underlying causes.

Vomiting may be short term — like that caused by motion sickness, gastroenteritis or food poisoning. However, sometimes you will not know exactly what caused an episode of vomiting.

Other causes can give rise to recurrent or ongoing vomiting, which need to be investigated by your doctor or may justify a visit to a hospital's emergency department. See vomiting to find out when you should seek urgent medical help for vomiting.

For information on the underlying causes of vomiting in children 12 years and under, see vomiting in children.

A sudden isolated bout of vomiting is known as ‘acute’ by doctors. A pattern of ongoing or recurring vomiting is known as ‘chronic’. The different underlying causes of vomiting are usually categorised into acute or chronic causes.

What causes acute vomiting?

Gastroenteritis

An infection of the digestive tract, such as gastroenteritis, is one of the most common causes of nausea and sudden vomiting. It is often caused by a virus, such as norovirus (the ‘winter vomiting bug’) or rotavirus. However, it may be caused by bacteria, such as Salmonella, Shigella or Campylobacter, where it is associated with ‘food poisoning’. This is known as having a ‘stomach bug’. Diarrhoea and abdominal pain are often accompanying symptoms.

Food poisoning

Some bacteria can cause food poisoning due to toxins (poisons) they secrete into food that is not stored properly. Bacillus cereus and Staphylococcus aureus are examples of these. The bacteria themselves may be destroyed by cooking or reheating, but their toxins will remain. Symptoms (most commonly vomiting) start quickly — 30 minutes to 6 hours after eating.

Poisoning

Poisoning most commonly occurs in young children, who often learn about things by putting them in their mouths. Many household items are poisonous if swallowed. Symptoms of poisoning include nausea and vomiting, drowsiness, fits (seizures) or breathing difficulties.

If you think a child has swallowed a poisonous substance or someone has taken an overdose contact the Poisons Information Centre by phoning 13 11 26 for advice (24 hours).

Do NOT attempt to make the child vomit, unless instructed by a medical professional.

Motion sickness

Motion sickness is more common in children than adults, but can be the cause of vomiting in adults. It may also cause paleness and cold sweats.

Alcohol

Drinking excess alcohol frequently results in nausea and vomiting. If you consume too much alcohol, alcohol poisoning may result.

Post-operative

At least one-third of adults experience nausea and vomiting after surgery, known as post-operative nausea and vomiting. Anti-emetic medicines may be given to treat or prevent this.

Gastrointestinal obstruction

An obstruction in your digestive tract will cause vomiting. It often begins without nausea. Depending on where the obstruction is, you may vomit bile, faecal material or partly digested food. Seek urgent medical help if you have symptoms of obstruction.

Appendicitis

Appendicitis can cause both nauseaand vomiting. Appendicitis usually causes a dull pain that starts around the belly button. The pain normally travels to the lower right of the abdomen where it is felt as a sharp pain. Other symptoms that may be felt are a loss of appetite, fever or chills.

If left untreated the appendix can become swollen and infected, and then burst. Urgent surgery is usually the treatment for appendicitis.

If you are concerned that you may have appendicitis you should immediately see your doctor or go to the emergency department or call an ambulance on triple zero (000).

Pancreatitis

Pancreatitis is inflammation of the pancreas. It usually causes abdominal pain, vomiting and fever. It can be very severe, even life-threatening.

Raised intracranial pressure

Raised pressure in the skull is a medical emergency and can cause nausea and vomiting. Riased intracranial pressure can be due to a head injury, meningitis or a tumour. The vomiting may be worse in the morning and may be projectile.

Meningitis

Symptoms of meningitis can happen suddenly, and include vomiting, fever, headache, a stiff neck, pain when looking at bright lights (photophobia), and sometimes a red or purple rash that doesn’t go away when you gently press on it.

Call triple zero (000) for an ambulance or go straight to the emergency department if you or a child is showing symptoms of meningococcal infection.

COVID-19

Nausea, diarrhoea and vomiting can all be symptoms of COVID-19. Some people with COVID-19 may only have gastrointestinal symptoms — with no respiratory symptoms during their illness. In others, gastrointestinal symptoms may occur before any respiratory symptoms do.

Diabetic ketoacidosis

Vomiting can be a symptom of diabetic ketoacidosis, where there is not enough insulin for the body to break down sugar. This is a medical emergency and can be fatal.

What causes chronic vomiting?

Medicines

Vomiting can be a side effect of some medicines. Examples of medicines that can cause vomiting are NSAIDs, nicotine replacement therapy, anti-arrhythmics (medicines that suppress abnormal heart rhythms), metformin (a diabetes medicine), some antibiotics and anticonvulsants. If you suspect that a medicine is causing vomiting, see your doctor or pharmacist. They can advise you and may be able to substitute it with another medicine.

Chemotherapy medicines

Nausea and vomiting can be a side effect of chemotherapy. These symptoms usually start a few hours after treatment. Tell your nurse or doctor if you experience these side effects. They may be able to give you medicine to stop the vomiting (antiemetic medicines).

Radiation treatments

Nausea or vomiting can be a side effect of radiotherapy. If you suffer from nausea or vomiting after treatments, tell the radiation oncologist or nurse. They may be able to give you antiemetic medicines to stop the symptoms.

Vitamins

High doses of vitamins can cause vomiting, so remember to tell your doctor about everything you are taking, including herbs, vitamins and other complementary medicines.

Pregnancy

Morning sickness is common during early pregnancy. It involves nausea and vomiting at any time of the day, but often in the morning. Usually, symptoms improve after the first 3 months of pregnancy. Hyperemesis gravidarum is an uncommon condition that causes severe and ongoing vomiting in pregnant women, leading to dehydration, electrolyte abnormalities and weight loss.

Migraine

Nausea and vomiting are common symptoms in the headache phase of a migraine, after the aura — if there is one.

Food allergies

Food allergies can cause ongoing digestive symptoms including vomiting, diarrhoea, constipation, flatulence (farting) and bloating. If you have symptoms shortly after eating see your doctor.

Upper digestive tract disorders

Vomiting after meals can be caused by GORD or gastrointestinal obstruction.

Gastroparesis

Gastroparesis is a delayed emptying of the stomach due to nerve damage. It can lead to nausea and vomiting after meals.

Kidney stones

Nausea and vomiting are symptoms of kidney stones, along with gripping pain in the back.

Functional nausea and vomiting

Functional nausea and vomiting is the name given to chronic nausea and vomiting for which there is no clear medical cause. Cyclic vomiting syndrome is a rare syndrome that is a type of functional nausea and vomiting. Episodes of vomiting, which last around 6 days, happen a few times a year. In between episodes a person will not have any symptoms. Long term use of cannabis can cause this condition. Functional vomiting is another classification, where a person has one or more episodes of vomiting per week.