Causes of Diarrhea
That You Should Know About

Causes of Diarrhea - Woman in pain

There are many different causes of diarrhea. Diarrhea normally happens when either extra water is secreted into your bowel or the fluid in partly digested food cannot be absorbed, but why does this happen? What causes diarrhea ?

Uncomplicated or non-serious diarrhea could simply be the result of eating some food that has upset the digestive system whereas complicated diarrhea could be indicative of a wide range of serious disorders of the gastro-intestinal system.

We have all known the misery of diarrhea and the average adult will have diarrhea four times a year and children will suffer from diarrhea 7-15 times before they are five. These numbers of course will be much higher in developing countries. 

Keep reading to find out more information about what might be causing your problem bowel movements.

Acute or Short Term Causes of Diarrhea

One of the most common causes of diarrhea is a bowel infection (gastroenteritis) which can be caused by either bacteria, viruses or parasites which can contaminate our food, water and our environment.


We are surrounded by bacteria. They live inside us and all around us and mostly they do not cause us any harm and some are even beneficial but certain bacteria can make us ill especially if they get a chance to multiply in food which is undercooked or not stored at the correct temperature.

These bacteria will make you ill given the chance:

Bacteria love warm conditions. They will be killed by heat and they will find it very hard to grow in cold conditions but they will grow very successfully in your warm kitchen, so do not leave food out of the fridge for too long. They also hate dry conditions and will grow much more easily when moist so contaminated water is one of their ideal environments.

They will also multiply on your kitchen counter top if it is not cleaned regularly with an anti-bacterial cleaner. They can also live on your hands, so washing hands properly with soap and warm water is very important.


Viruses are much smaller than bacteria and unlike bacteria they cannot multiply by themselves, they have to find a living host cell. However, they can survive outside the body sometimes for several days or longer and will then multiply very quickly once ingested.

You only need to ingest a very tiny amount of the virus to become infected. There are no beneficial viruses. If you come into contact with infected particles of feces or vomit you are likely to become ill. This is can happen if you touch contaminated surfaces and then touch your mouth or nose. This can be as easy as shaking hands with someone who has recently been infected or touching a door handle or contaminated telephone.

Causes of diarrhea include common viruses such as:

  • Norovirus (Causes 90% of large scale outbreaks amongst adults)
  • Rotavirus (Very common amongst children, most adults have acquired immunity)
  • Adenovirus
  • Astrovirus


Parasites are one of the causes of diarrhea and can enter the intestinal system through contaminated water or food.
Common diarrhea causing parasites are:

  • Giardia lamblia
  • Cryptosporidium
  • Entamoeba histolytica

Exposure to parasites is more likely with international travel although it should not be ruled out in other circumstances.

Food Poisoning

Causes of Diarrhea - Man in Pain

One of the common causes of diarrhea is food poisoning which is a gastroenteritis specifically caused by eating contaminated food.

Researchers using data from the US Centers for Disease Control and Prevention found that the percentage of food poisoning outbreaks and illnesses caused by different contaminated foods were as follows:

  • 46% fruits, nuts and vegetables and of these 22% were attributable to leafy vegetables like salad.
  • 22% were caused by meat and poultry
  • 14% dairy
  • 12% fruits and nuts
  • 10% poultry

Dairy foods caused the most hospitalizations followed by leafy vegetables, poultry, vine vegetables (like tomatoes and cucumber), stalk vegetables like asparagus and then fish and seafood.

Poultry was responsible for the greatest number of deaths (19%) followed by dairy (10%), vine/stalk vegetables (7%), fruit-nuts (6%) and leafy vegetables (6%).This sounds very scary but the majority of the food we eat is safe, it is the improper preparation and storage of that food that is usually to blame for food poisoning.

The best way to prevent being infected and contracting gastroenteritis is to avoid poor hygiene. Wash hands thoroughly especially after visiting the bathroom, changing diapers (nappies), and before preparing food. Clean kitchens and bathrooms regularly, cook food thoroughly and store in a fridge at the correct temperature (at or below 40oF or 4oC)

Be particularly careful when preparing foods that cause diarrhea the most like chicken.


Medicines can be one of the diarrhea causes. Some common ones that can cause this problem are listed below but the list is not exhaustive. Check on the leaflet that comes with your medication for possible side effects.

  • Antibiotics. (A common cause because antibiotics can affect the ‘good’ bacteria which inhabit our intestines. This is not usually serious but may precipitate C. diff which can be very dangerous)
  • Chemotherapy medicines
  • Laxatives
  • NSAIDs used to treat arthritis and pain
  • Immunosuppressant’s
  • Drugs used to treat heartburn and stomach ulcers (particularly antacids containing magnesium)
  • Propranolol
  • Metformin
  • Diuretics like furosemide
  • Corticosteroids
  • Antidepressants

Functional Bowel Disorders

One of the common diarrhea causes is functional bowel disorders. This means that the bowel itself is healthy and no sign of disease can be found when tests are done but the functioning of the bowel is disrupted.

The most commonly diagnosed functional bowel disorder is irritable bowel syndrome. The exact cause of this disorder is still open to debate but a defining feature is that the diarrhea will not occur during the night when the person is sleeping.

A similar disorder to IBS among young children is toddler diarrhea. Transit times in this disorder are too fast, resulting in frequent diarrhea in an otherwise healthy child.

Intestinal Disorders

Diarrhea can be a symptom of many disorders.


Chronic diarrhea can sometimes happen following surgery such as:

  • Gastrectomy (removal of part of the stomach)
  • Bariatric surgery (for weight loss)

Other Causes of Diarrhea

Most cases of diarrhea will only last 24-48hrs and do not require medical treatment but if your diarrhea is prolonged or you have other symptoms like blood, fever, severe abdominal or rectal pain, black tarry stools or dehydration then contact your doctor. Elderly people or babies and children should see a doctor more quickly than adults.

The causes of diarrhea are many but mostly they are not worrisome. If however you are worried then talk to your healthcare practitioner. Many people feel embarrassed to have this symptom but I have nursed many people suffering like this and have suffered myself in the past with irritable bowel syndrome and so I know how you are feeling.

This is something that every person has had more than once and is something that healthcare workers take in their stride. I hope you have found this information dealing with causes of diarrhea helpful. If you would like more help and information you can find more details by exploring 

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