Why Do We Get Diarrhea?

The Causes and Why Our Bodies React the Way They Do

Diarrhea. We all get it from time to time, but no one wants to talk about it. It's embarrassing, uncomfortable, and gross. But have you ever thought about why we get it? Sometimes it's due to the foods we eat, sometimes it's caused by a virus or bacteria and other times it could be caused by a disease that affects the digestive system itself. Here, we'll talk about some of the most common causes of diarrhea and what exactly happens to our bodies when we get it.

An adult with an arm around a child on a virtual doctor's visit

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Some of the most common causes of diarrhea are viral infections. Norovirus, rotavirus, and hepatitis A are all viruses that frequently cause diarrhea. Rotavirus is the most common cause of diarrhea in children in the world. However, the introduction of a vaccine to prevent it in the US has dramatically reduced the number of cases in the country in recent years.


Diarrhea can be caused by several types of bacteria. Some of the most common causes of food contamination or "food poisoning" are bacterial. E. coli, salmonella, campylobacter, and listeria are all frequent culprits and cause for recalls when they are found in our food supply.

Although these bacteria cause diarrhea (and occasionally vomiting), most people who get them recover without treatment. In some severe cases, people with these infections may need to be treated with antibiotics or hospitalized.

Digestive System Diseases and Disorders

Some people get diarrhea due to diseases and disorders of the digestive system. Some examples include:

The exact reason for diarrhea varies if you have one of these disorders or diseases. Treatment will depend on the cause as well. If you are concerned your diarrhea might be caused by one of these diseases or disorders, talk to your healthcare provider.

Other Causes

Diarrhea can be caused by parasites such giardia as well. This parasite gets into the digestive tract and affects the absorption of fluids, resulting in frequent watery stools.

Another frequent cause of diarrhea is as a side effect of medications — especially antibiotics. If you take an antibiotic and it causes diarrhea, talk to your healthcare provider to determine whether or not it is something you should be concerned about.

Traveler's diarrhea occurs when people travel to other countries around the world and eat their food or drink their water because it is more likely to be contaminated with bacteria, viruses or parasites.

This is not a concern when traveling to most developed countries but is a frequent problem for people that visit most countries in Asia (other than Japan), Africa, Latin America, and the Caribbean. If you will be traveling to one of these areas, talk to your healthcare provider about taking medications with you to treat infections should they occur.

When you have diarrhea caused by a germ—whether it's a bacteria, virus or parasite, the normal function of your body's GI system is disrupted. The stool is what is left over after your body has digested all of the fluid and nutrients it needs from the food you eat. When you get an infection that disrupts that function, your GI systems doesn't absorb nutrients and fluids adequately and it passes through your body more quickly than it should, leading to frequent, watery bowel movements.

Frequently Asked Questions

  • Why do I have diarrhea when I am not sick?

    People can have episodes of loose stools without being sick. This can come from a change in diet, stress, or a side effect of medication. An occasional episode of loose stools is normal. Diarrhea is defined as having three or more episodes of loose stools in a 24-hour period.

  • Is diarrhea a symptom of COVID?

    Yes, diarrhea is sometimes a symptom of COVID-19. The pandemic coronavirus causes a wide variety of possible symptoms and certain strains of the virus are more likely to cause diarrhea, nausea, and vomiting than others.

    Other COVID symptoms include fever, chills, headache, muscle and body aches, congestion, sore throat, cough, shortness of breath, and loss of taste or smell. 

  • What are the main causes of diarrhea?

    Diarrhea is commonly caused by a viral infection, just as norovirus or rotavirus. Food poisoning from bacteria—like E. coli, salmonella, or listeria—can also cause diarrhea. 

    Digestive system disorders can also cause chronic diarrhea. These include celiac disease, Crohn’s disease, colitis, food intolerances, pancreatitis, and small intestinal bacterial overgrowth. 

    Diarrhea can also be caused by a parasite or be a side effect of medications or supplements. 

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Crawford SE, Ramani S, Tate JE, et al. Rotavirus infectionNat Rev Dis Primers. 2017;3:17083. doi:10.1038/nrdp.2017.83

  2. U.S. Department of Health & Human Services. Food Poisoning.

  3. National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & Causes of Diarrhea.

  4. Centers for Disease Control and Prevention. Giardia.

  5. Centers for Disease Control and Prevention. Travelers' Diarrhea.

By Kristina Duda, RN
Kristina Duda, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.