Sudden Onset Vomiting and Diarrhea Causes and Dangers

We have all experienced food poisoning or the stomach flu at some point in our lives. Symptoms can arise suddenly and be very severe. From nausea that intensifies within minutes to violent bouts of vomiting and explosive diarrhea, these symptoms are not uncommon with food poisoning or the stomach flu.

However, not every instance of vomiting and diarrhea that arises suddenly is due to food poisoning of the stomach flu. There are many other possible causes and some of these conditions can be life threatening. It is therefore important that sudden onset vomiting and diarrhea is assessed by a doctor to identify the exact cause.

How Vomiting and Diarrhea Start?

Vomiting is a forceful mechanism to push out any toxins or irritants from the upper gut. The small muscles in the gut normally contract and relax in a coordinated manner to push food and fluid downwards from the mouth to the bowels. This movement is known as peristalsis and starts from the esophagus the moment we swallow. It is essential for food to be digested, nutrients absorbed and wastes expelled from the bowels.

However, when the vomit reflex is trigger this pushing direction reverse. The reverse peristalsis along with increased abdominal pressure pushes any food, fluids or other substances in the small intestine and stomach into the esophagus and out of the mouth as vomitus. Apart from irritants and toxins in the gut, vomit centers in the brain can also initiate the vomiting process.

Diarrhea is similar in some respect. Irritants and toxins in the bowels can initiate diarrhea. This may be due to drawing out water from the body into the bowels, speeding up movement within the bowels (peristalsis) or injury the bowels. As is the case with vomiting, the central nervous system can also stimulate rapid bowel movements and lead to diarrhea without any problems within the bowels.

In most cases where there is vomiting and diarrhea, the irritant enters through food and water. It first disrupts the upper gut leading to nausea and vomiting. As the irritation extends lower down the digestive tract, diarrhea subsequently arises. Eventually the vomiting may subside while the diarrhea continues.

When are vomiting and diarrhea serious?

Vomiting and diarrhea are two common ailments. It is frequent in life that is often not due to any serious cause if the vomiting is once off or the diarrhea only lasts for a day. However, vomiting and diarrhea can be due to serious and even deadly causes. Therefore it is important to understand when vomiting and diarrhea be considered as serious. The following characteristics of vomiting and diarrhea or the presence of other symptoms may be an indication of severe disease.

  • Persistent vomiting for more than a few hours which is not abating.
  • Inability to hold down fluids.
  • Vomiting up blood or bloody vomitus (hematemesis).
  • Blood or bloody stool in diarrhea.
  • Abnormally low blood pressure or high heart rate.
  • Confusion.
  • Loss of consciousness.

The most common complication of both vomiting and diarrhea is dehydration. This can set in quickly. Dehydration can be life threatening if not treated and managed properly.

Causes of Sudden Vomiting and Diarrhea

Many of the causes below may result in both vomiting AND diarrhea, however, at other times it could only cause vomiting OR diarrhea. The development of symptoms may be linked to the intensity or severity of a condition or concentration of exposure to toxins and may only cause nausea and loose stool.

Infections and Inflammation

Various inflammatory conditions can lead to sudden onset vomiting and diarrhea. This inflammation may or may not be due to an infection. The digestive tract is the most likely area to be affected but sometimes the brain is affected and this lead to vomiting and diarrhea.

  • Appendicitis
  • Gastroenteritis
  • Malaria
  • Meningitis
  • Opportunistic infections in immunocompromised patients (HIV/AIDS, cancer, use of immune suppressants)
  • Peritonitis
  • Septicemia


Sudden onset vomiting after a head injury should always be treated seriously and investigated immediately. Similarly diarrhea, particularly bloody diarrhea, after abdominal injury could be a serious sign.

  • Closed head injury
  • Abdominal injury
  • Injury to the spinal column
  • Any cause of severe pain


Certain drugs may cause vomiting and diarrhea as side effects. Some of these drugs may not always directly cause vomiting and diarrhea but instead lead to other side effects from which vomiting and diarrhea may ensue.

  • Antibiotics
  • Certain types of antacids
  • Cytotoxic agents – chemotherapy for cancers
  • Laxatives
  • Narcotic drugs
  • NSAIDs
  • Proton pump inhibitors (PPIs)

Foods and Drinks

Certain foods and drinks may be irritants or toxins. At other times the body may be unable to digest certain foods and beverages thereby resulting in vomiting and diarrhea shortly after consumption.

  • Indigestible foods and fluids
  • Food allergies, intolerance
  • Food poisoning/intoxication and food infection
  • Excessive alcohol intake

Environmental, Pollution and Poisoning

A host of environmental factors can lead to sudden onset vomiting or diarrhea. This is largely due to toxicity and unintentional poisoning. However, at this there is intentional poisoning and this should be investigated further.

  • Bites and stings – snakes, spiders, and other insects
  • Contaminated food and water may contain bacterial toxins and other microbes as well as toxins, industrial chemicals and poisons.
  • Gases – air pollution by factories
  • Heavy metals – thallium, cadmium, arsenic poisoning
  • Herbal supplements used for purging
  • Nicotine – excessive cigarette smoking, use of tobacco or nicotine replacement products
  • Oils like castor oil
  • Plant toxins
  • Scombrotoxic, ciguatera fish poisoning or paralytic shellfish toxin caused by dinoflagellates.
  • Swimming pools – ingestion of chlorinated water
  • Radiation exposure

Pain and Psychogenic

Sometimes vomiting and diarrhea may not arise for obvious reasons like disorders and diseases within the bowels. Instead it is a response to extreme stress to the body, as may be seen with severe pain. It can also arise due to psychological stress.

  • Eating disorders
  • Headaches and migraines
  • Intense emotions – anxiety, excitement, fear
  • Any cause of severe pain like kidney stones.

Read more on stress diarrhea.


Several other diseases and disorders must be investigated as a possible cause of sudden onset vomiting or diarrhea. Some of these conditions can be serious and even life threatening, such as vomiting which may occur with a heart attack.

  • Diabetic ketoacidosis
  • Excessive/strenuous physical activity.
  • Heart attack
  • Gastric bypass surgery, intestinal resection
  • Violent, vigorous motion
  • Pregnancy
  • Uremia

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