Common Causes of Diarrhea

Few things are more urgent than the need to go. Unfortunately, diarrhea not only results in urgency, but it can also send you running to the bathroom multiple times–and may be the direct result of a stomachache. Diarrhea itself is pretty common, with an estimated 179 million cases of acute diarrhea occurring in the United States each year.

The causes behind diarrhea, however, are various. Your runny bowels may be caused by something as simple as your diet or more complicated psychological factors like stress. It may also be a symptom of an intestinal condition, such as inflammatory bowel syndrome (IBS) or inflammatory bowel disease (IBD), or other causes of varying severities. Thankfully, most cases of diarrhea go away within a few days. Even persistent and chronic types can often be managed with the proper treatment.

Learn about the common causes of diarrhea and how to identify what’s causing those loose, watery bowel movements.

In this article:

Diarrhea: Definition and impact

Diarrhea is having three or more loose, watery stools in a day. It can be acute, persistent or chronic. Diarrhea can have a massive impact on life and productivity. It can also lead to malnutrition—and, in worst cases, death.

Common causes of acute diarrhea

Acute diarrhea is a sudden bout of loose, watery stools that usually lasts no longer than two weeks. However, most cases resolve within one to two days.

It’s the most common type of diarrhea and typically responds well to OTC anti-diarrheal medicines, like loperamide and bismuth subsalicylate. But be sure to check with your health care provider before taking antidiarrheal medications for acute diarrhea.

The most common acute diarrhea causes include these:

Infectious agents

While stress and anxiety can sometimes be the cause, Infections, such as viral gastroenteritis, are the most common cause of acute diarrhea. Some viral infections include rotavirus, which can cause watery diarrhea and vomiting in children, and norovirus, the leading cause of vomiting, diarrhea and foodborne illness in the United States. Parasitic and bacterial infections may also cause acute diarrhea.

You can also get infections from food poisoning, where bacteria and parasites enter your body through contaminated food and water. Once the microbes reach the gut, they multiply and release toxins into the intestines, leading to diarrhea.

Medication side effects

Many medications can cause diarrhea, each through different mechanisms. For instance, the magnesium in antacids can cause or worsen diarrhea. Antibiotic-associated diarrhea can be caused by an overgrowth of harmful bacteria.

Some medications speed up the digestive process, allowing less time for water and nutrient absorption from the gut, while others affect fat and carbohydrate absorption or breakdown.

Common Causes of Chronic Diarrhea

Chronic diarrhea is defined as a persistent alteration of stool consistency from the norm with loose stools and increased stool frequency of greater than three stools daily for at least four weeks. If diarrhea extends to greater than 14 days, it is persistent diarrhea. It is chronic when the duration is more than 30 days. As the diarrhea becomes persistent, it becomes more likely that the cause of the diarrhea is non-infectious. Unlike acute diarrhea, chronic diarrhea is less likely to go away on its own and often requires a diagnosis. This type of diarrhea is often classified into three types:

• Fatty or malabsorptive: Stools tend to be greasy, bulky and smellier than normal and leave oil residue in the toilet. This happens because the body can’t properly digest or break down fats.
• Inflammatory: These stools are often frequent, small in volume, and bloody. It usually results from an inflamed and damaged gut lining.
• Watery: These stools are loose and watery. This happens when the colon can’t reabsorb water and electrolytes from your stool.

Some of the most common chronic diarrhea causes include the following.

Irritable bowel syndrome

Irritable bowel syndrome is a common condition that affects about 10 to 15% of Americans. It causes bloating, tummy pain or discomfort, and changes in bowel movement. While IBS causes symptoms, there are typically no signs of disease or damage in the gut.

IBS can cause diarrhea, constipation or a combination of both. If you have IBS-D, also called IBS diarrhea-predominant, more than a quarter of your stool is loose or watery, and the rest may be hard or lumpy.

Inflammatory bowel disease

Inflammatory bowel diseases (IBD) are conditions that cause recurring inflammation and damage to the intestinal tract. In IBD, the immune system mistakenly attacks healthy gut tissue, causing irritation and ulcers (open sores) on the gut lining. Look for these symptoms of IBD:

• Stomach cramps
• Chronic diarrhea
• Blood in poop
• Urgency to poop
• Unintended weight loss

There are two types of IBD: Crohn’s disease and ulcerative colitis.

In Crohn’s disease, inflammation affects the deepest layers of the intestinal walls. As it can affect any part of the GI tract, it can affect the small and large intestines. Its most common symptoms are diarrhea, abdominal cramps or pain and weight loss. However, a person’s symptoms may vary depending on which part of the GI tract is affected and how severe the inflammation is.

Ulcerative colitis only affects the large intestines. Its most common symptoms are abdominal pain and stool with pus or blood. In contrast to Crohn’s disease, which has patchy areas of inflammation with sections of healthy gut in between, the inflammation in ulcerative colitis is widespread and continuous.

Celiac disease

Celiac disease is an autoimmune condition affecting the small intestine. It is triggered by gluten consumption. Consuming gluten causes the immune system to attack the villi lining the small intestine, which are responsible for nutrient absorption. This leads to changes in bowel habits, malabsorption, malnutrition, and overall poor health.

Celiac disease is different from gluten sensitivity. While they share symptoms, gluten sensitivity does not trigger an autoimmune response and does not damage the small intestine.

Lactose intolerance

Lactose intolerance causes abdominal cramping, diarrhea, and sometimes constipation after eating foods or liquids containing lactose, a sugar naturally found in milk products. The condition happens when the small intestine has a limited amount or even none of an enzyme called lactase, which is required to break down the lactose. A person with lactose intolerance will typically experience symptoms 30 minutes to 2 hours after consuming products with lactose.

Microscopic colitis

Microscopic colitis is a type of IBD that causes swelling and inflammation in the inner lining of the large intestine. It commonly causes persistent watery, non-bloody diarrhea. Doctors can’t see the inflammation of microscopic colitis during a colonoscopy. The inflammation only becomes evident when they examine a tissue sample under a microscope, called a biopsy.

Anyone can develop microscopic colitis, but it’s more common in older adults. It is also three to nine times more common in women.

Dietary causes of diarrhea

Eating certain types of food may upset the digestive system and lead to diarrhea. Fiber has many digestive and gut health benefits, but consuming too much or suddenly increasing your fiber intake can lead to diarrhea.

Fried and fatty foods can also sometimes contribute to dietary diarrhea. They’re difficult for the body to digest, so they pass into the colon. Fatty acids in the colon cause the organ to secrete more water, leading to loose, watery stools.

Artificial sweeteners take time to be absorbed by the body and can cause diarrhea if consumed in large amounts. Other foods that may cause diarrhea are caffeine and spicy foods.

Another significant food grouping that can cause diarrhea is FODMAPs, which stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. FODMAPs are short-chain carbohydrates that the digestive tract can’t fully digest and absorb. They increase water content in the small intestines and can cause excessive gas production. This can lead to symptoms of bloating and diarrhea.

Traveler’s diarrhea

Traveler’s diarrhea happens when you visit places where food and water may be contaminated. While it can happen anywhere, more cases occur in certain higher-risk regions.

Help reduce your risk of getting traveler’s diarrhea by introducing these measures into your travel routine:

• Only eat foods that are served hot and fully cooked.
• Thoroughly wash raw fruits and vegetables in clean water.
• Drink factory-sealed beverages.
• Avoid street food or food sitting in a buffet.
• Avoid ice.
• Don’t use tap water for drinking or brushing your teeth.
• Frequently wash your hands with soap and water or use an alcohol-based sanitizer if water and soap are unavailable.

Diarrhea in children

Diarrhea is a very common problem affecting young children. It is also the third leading cause of death worldwide in children under 5 years old. Children often get acute diarrhea from schools and daycare. Meanwhile, they may get chronic diarrhea from diseases that cause malabsorption and inflammation.

For mild diarrhea,  children should be kept hydrated with enough fluids. For infants, continue feeding them with breast milk or formula.

Aside from adequate hydration, older children can be given oral rehydration solutions (ORS). Fruit juices and soft drinks should not replace ORS, as juices and soft drinks can worsen the condition. In cases of severe diarrhea, doctors may need to administer fluids intravenously in a hospital.

Diarrhea in older adults

Bowel symptoms are more common in older people than in the general population. This is probably because aging affects many gastrointestinal (GI) functions, including digestion, transit time, and absorption. They are also more likely to develop GI problems from certain medications.

Staying physically active, getting adequate hydration, eating a healthy diet, and maintaining a healthy weight can all help keep an older adult’s digestive health in shape.

It’s also best to talk to a doctor if you’re taking medications that may cause diarrhea so they can recommend alternatives. Examples of these drugs can include laxatives, antacids, antibiotics, anti-diabetes medications, and anticonvulsants.

Rare but serious causes of diarrhea

Diarrhea is often not a cause for concern. But sometimes, it can signify a more serious health issue. In rare cases, chronic diarrhea can be a symptom of more serious conditions, such as these:

Pancreatic disorders

The pancreas creates digestive juices that digest food. If you have conditions like pancreatitis or pancreatic cancer, you may experience diarrhea or an upset stomach and pass greasy, bad-smelling stools. This happens because of the lack of digestive enzymes needed to properly break down food, leading to malabsorption.

Hormonal disorders

Diarrhea can also be a symptom of endocrine diseases like hyperthyroidism or diabetes. Hyperthyroidism overstimulates the sympathetic system, causing GI tract symptoms like diarrhea. Meanwhile, one in five people with diabetes experience diarrhea as a complication.

Colorectal cancer

A change in bowel habits can be one of the telltale signs of colorectal cancer. Signs may be a narrowing of the stool or more frequent diarrhea or constipation. Other symptoms include a strong urge to poop, blood in your stool and unexplained weight loss.

Diagnosing the cause of diarrhea

Most cases of diarrhea are self-limiting and don't need intervention. However, if it’s persistent or causing worrisome symptoms, your health care provider will work to find the cause and provide you with the most appropriate treatment.

They will use information from your history, physical exam, and lab and imaging results to determine the cause of your diarrhea.

Medical history and physical examination

Your health care provider should ask about your symptoms, including the consistency, color, volume, frequency, and duration of your bowel movements. They will also ask about the following:

• medications you’re taking
• foods and drinks you consumed
• recent travel
• contact with other people who are sick

They may also ask if anyone in your family has been diagnosed with celiac disease, IBS, IBD or food allergies and intolerances.

Then, your provider may perform a physical exam to look for other symptoms that may explain what’s causing your diarrhea and check for complications like dehydration. The exam may include checking your vital signs, examining your abdomen, doing a digital rectal exam to check for blood in your stool, and other relevant evaluations.

Laboratory tests

Your provider may order some lab tests to help them determine the cause of your diarrhea. This often includes a stool test to check for parasitic or bacterial infections, as well as blood tests to rule out diseases and disorders.

They may also order additional tests specific to their suspected cause, such as these:

• Hydrogen breath test: measures the hydrogen in your breath to see if you have lactose intolerance
• Fasting tests: to know if you have trouble digesting certain foods (intolerances) or if they trigger an immune reaction (allergies)
• Elimination tests: to see if eliminating specific foods helps relieve your diarrhea
• Imaging tests: to look for abnormalities in the structure of your organs
• Endoscopy: looks at the inside of your digestive tract to find out what’s causing your diarrhea.

Understanding the root of your diarrhea

While most diarrhea resolves within a day or two, the condition may sometimes persist, causing discomfort and disrupting daily activities. Sometimes, it can also be a warning sign of a more serious problem.

Identifying the root cause of your diarrhea is crucial to help find the right treatment and to make dietary and lifestyle changes to prevent its recurrence.

Severe diarrhea can lead to severe dehydration. Seek medical attention immediately if you experience signs of dehydration, such as dry mouth, dizziness, and lack of urine, or if you have any of the following symptoms:

• Fever
• Severe pain
• Frequent vomiting
• Stool with blood or pus

Frequently Asked Questions

When should you worry about diarrhea?

Generally, if diarrhea lasts longer than two days, causes dehydration, or is accompanied by fever, abdominal pain, vomiting, or stools with blood or pus.

How long should diarrhea last in adults?

It depends. Diarrhea caused by infections typically lasts within one to two days. Meanwhile, diarrhea as a result of chronic conditions caused by malabsorption and inflammation typically extends beyond 14 days.

What stops diarrhea fast?

It depends on the cause. Diarrhea caused by infections may resolve on its own, and taking medications to stop infectious diarrhea may be harmful. Diarrhea caused by food allergies and intolerances usually improves once the allergen or offending food is removed. Drinking plenty of water and taking OTC medications recommended by a health care provider can also help stop diarrhea faster. Review product labels and use them as directed on the package.

What are the major causes of diarrhea?

The major causes of diarrhea include infections, certain medications, specific foods, and digestive disorders, such as inflammatory and malabsorptive disorders.

This content is for informational purposes only and is not medical advice. Consult your health care provider before taking any vitamins or supplements and prior to beginning or changing any health care practices.