What are the Most Common Causes of Watery Diarrhea?

Dee Saale
Dee Saale

There are many different causes of watery diarrhea. The most common reasons include viral or bacterial infections. Certain medications and food intolerances may also cause this condition. In addition, certain medical problems, such as mal-absorption, hyperthyroidism, and diabetes may cause diarrhea. People who abuse laxatives or alcohol may also have bouts of diarrhea.

People who are intolerant toward the gluten found in wheat can suffer from digestive problems.
People who are intolerant toward the gluten found in wheat can suffer from digestive problems.

Viral and bacterial infections that affect the stomach and intestines are the main causes of watery diarrhea. For example, viral gastroenteritis, or the "stomach flu," usually causes diarrhea, among other symptoms. There are a handful of viruses, such as the norovirus, the rotavirus, and the adenovirus, that can cause the catch-all illness, stomach flu. Some viruses, such as rotaviruses, affect mainly children, while others, such as noroviruses, affect people of every age.

Salmonella, a common cause of food poisoning, can cause diarrhea.
Salmonella, a common cause of food poisoning, can cause diarrhea.

Food poisoning is the general name for bacterial infections caused by a wide range of bacteria. For example, campylobacter is a bacterial infection that causes diarrhea when a person drinks unpasteurized milk that has been contaminated. Salmonella is another kind of bacterial infection that can cause diarrhea when a person eats bacterially contaminated, raw poultry or eggs. With bacterial infections, the diarrhea is the body’s mechanism for getting the harmful bacteria out of the body.

Diarrhea that lasts for more than two days may be a symptom of a serious condition.
Diarrhea that lasts for more than two days may be a symptom of a serious condition.

Food intolerance and food allergies are also causes of watery diarrhea. People can be intolerant toward dairy, yeast, gluten, or even sugar. In addition, some people may have a food allergy toward a specific food. In those cases, the person can avoid diarrhea and other issues by avoiding the offending foods.

Sometimes starting a new medication or taking a certain medication or supplement may cause diarrhea. For example, antacids and supplements containing magnesium are common culprits of watery diarrhea. Also, nonsteroidal anti-inflammatory drugs, antibiotics, chemotherapy drugs, and high blood pressure medications may lead to diarrhea.

Other causes of watery diarrhea include certain medical conditions. For example, people with substance abuse issues, such as those who abuse alcohol and laxatives, may have diarrhea. Other medical conditions that may cause a person to have diarrhea include diabetes and intestinal issues. Specifically, hypothyroidism and mal-absorption may cause people to have intestinal distress, such as diarrhea.

As with any medical condition, any concerns over watery diarrhea should be addressed by a medical professional. In some cases, the substance causing the diarrhea simply needs to be evacuated from the body. In other cases, medicine may be needed to help the stool become firmer. Regardless, in most cases, diarrhea should only last a few days. If it lasts longer, medical assistance should be sought.

Certain medical conditions may cause watery diarrhea.
Certain medical conditions may cause watery diarrhea.
Dee Saale
Dee Saale

Dee is a freelance writer based in Colorado. She has a B.A. in English Literature, as well as a law degree. Dee is especially interested in topics relating to medicine, legal issues, and home improvement, which are her specialty when contributing to wiseGEEK.

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Discussion Comments


I recall the watery diarrhea and vomiting I experienced when I got the stomach flu several times as a kid. I seemed to get it once a year, and I usually missed a week of school with it.

I would vomit and have diarrhea so much that there was nothing left but yellow bile and water. It baffled me how my body could continue to force me to eliminate these fluids when nothing solid even remained inside of me.

I still remember my mother having to insert a suppository to stop the vomiting and diarrhea. I told her that it would just come out with the diarrhea, but it melted rather quickly, and it did offer me some relief.


My husband is allergic to mushrooms. Every time he ate any, he had diarrhea that was watery and persistent, so he figured out what was causing the problem.

Significant cramping went along with the diarrhea. There was a lot of pain involved, so he learned to stay away from anything containing mushrooms.

Once, I bought some frozen egg rolls without checking the ingredient list. After he had already taken two big bites, he saw a piece of mushroom. I gave him a couple of antihistamines, and this prevented him from getting severe diarrhea, although he did have regular diarrhea.


@OeKc05 – Clear watery diarrhea is very scary. I ate some seafood at a restaurant once, and I had severe diarrhea within half an hour.

It started out looking normal, but I could not seem to stop, and it eventually turned clear. Eliminating fluids at such a rapid rate is very scary, but I had always heard that food poisoning would run its course, and I didn't need to see a doctor.

I drank plenty of water and electrolyte drinks. I still felt fatigued and washed out, but I stayed alive, and within two days, the watery diarrhea was gone.

I know that some cases of food poisoning are more severe than others, though. If I had been losing consciousness or hallucinating, I would have gotten help.


I had rotavirus as a child, and it caused severe watery diarrhea and vomiting. Both were so frequent that I was in grave danger of dehydrating, so my parents took me to the emergency room.

I had to have intravenous fluid to keep me hydrated. I remember having various shots and suppositories to control the vomiting and diarrhea. I recall having to vomit and run to the bathroom several times while waiting in the lobby.

I had to stay in the hospital for five days, and I wasn't allowed to have visitors other than my parents, because rotavirus was so contagious. The watery diarrhea was really scary before they got it under control, because it seemed that I had nothing more in me to excrete, yet it kept coming out.

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