What is diarrhea?

Diarrhea¹ refers to loose, watery stools and more frequent bowel movements. People with diarrhea generally experience abdominal pains or cramps, nausea, an urgent need to use the bathroom, and, occasionally, a loss of control of bowel movements.

Everyone is at risk to get diarrhea. It’s a common problem that most adults experience once per year, and most young children have twice per year.

Diarrhea can be caused by bacteria from contaminated food, viruses (such as the flu virus), parasites, food intolerances (such as lactose intolerance), certain medications, and a number of diseases and conditions that affect the stomach (including ulcerative colitis, a form of inflammatory bowel disease [IBD]).

Most cases of diarrhea are considered to be acute. Acute diarrhea is defined as having three or more loose stools in one day. Thankfully, this type of diarrhea is short-lived, lasting about one to three days. Acute diarrhea usually goes away on its own without the need for medication or treatment.

Though many people get over diarrhea quickly, it can, in some cases, prove to be a dangerous condition. This is because diarrhea depletes bodily fluids, which can lead to dehydration. Diarrheal diseases currently account for 1 in 9 child deaths worldwide².

In addition to dehydration, the duration of diarrhea can be a cause for concern. Diarrhea that lasts for more than a few days is typically an indication of another problem or a chronic condition, such as irritable bowel disease (IBD) or celiac disease.

Chronic diarrhea

Diarrhea can be acute (short-lived, lasting for only a few days), persistent (lasting 2–4 weeks), or chronic (persistent). Chronic diarrhea³ is defined as diarrhea that lasts for more than 4 weeks. People who experience chronic diarrhea may have symptoms that occur continuously or periodically, as this is often associated with an underlying health problem.

For otherwise healthy people, chronic diarrhea may only be a nuisance. For those with weakened immune systems, such as those living with HIV/AIDS or undergoing chemotherapy treatment, chronic diarrhea can cause life-threatening complications.

Depending on its cause, chronic diarrhea can signal a more serious underlying health problem. Recurrent diarrhea arises from a number of issues, including infections, food allergies and intolerances, use of certain medications, digestive tract conditions, and side effects of abdominal surgery.

Common causes of chronic diarrhea include⁴:

• Intestinal parasites (e.g., cryptosporidium, cyclospora, microsporidia)
• Bacterial infections (e.g., E. coli, salmonella, shigella)
• Viral infections (e.g., influenza, rotavirus, norovirus, COVID-19⁵)

• Fool allergies and intolerances, such as lactose intolerance
• Conditions that affect the digestive tract including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and celiac disease
• Unexplained conditions thought to stem from infections: One such example is Brainerd diarrhea, the name for a type of severe sudden-onset diarrhea that doesn’t respond to antibiotics and lasts for months. The cause of Brainerd diarrhea has not been identified.

Chronic diarrhea may also result from some types of abdominal surgery. Operations on the appendix (such as appendectomy, used to treat appendicitis), gallbladder, large intestine, liver, spleen, stomach, and other areas of the abdomen have all been known to cause chronic diarrhea.

Treatment is often necessary when chronic diarrhea arises from a viral or bacterial infection. In this case, the particular type of infection, virus, or bacteria causing diarrhea will determine the type of treatment to be used. If you have a tapeworm infection, for example, your healthcare provider may prescribe a type of antiparasitic drug known as an anthelmintic, such as praziquantel⁶ (generic Biltricide).

How common is diarrhea?

Diarrhea is very common⁷, with most people experiencing it once or twice per year. In the United States, there are 179 million cases⁸ of acute diarrhea each year. Additionally, according to the American Gastroenterological Association⁹, diarrhea affects up to 5% of the population at any given time.

Though most people overcome it without any major issues, some may experience serious complications as the result of diarrhea. Some potential issues associated with diarrhea include dehydration, electrolyte imbalance, malabsorption, and kidney failure. Those most at risk of developing severe and life-threatening complications from diarrhea¹⁰ include:

• Malnourished children
• Elderly individuals
• Those with preexisting medical conditions, especially those that impair immune function (called autoimmune disorders), can be at higher risk of developing infections. This, in turn, can increase their chances of experiencing diarrhea, as the body is not able to fight off infection as well as it should.
• Patients with HIV, who are at the highest risk of experiencing life-threatening diarrhea.

The incidence of death caused by diarrheal diseases is much higher in lower-income countries. Overall, diarrheal diseases cause more than 500,000 child deaths each year¹¹, making it the third leading cause of child mortality worldwide.

Considering that roughly 88% of diarrhea-associated deaths are linked to insufficient hygiene, unsafe water, and inadequate sanitation, public health experts attest that diarrhea is treatable and preventable as long as the necessary resources are available.

What causes diarrhea?

Because most cases of diarrhea pass without the need for medication or treatment, it’s typically not necessary to diagnose the underlying cause of diarrhea. The most common causes of acute and persistent diarrhea include infections, traveler’s diarrhea, and side effects of medication.

Some types of infections that can cause both acute and persistent diarrhea are:

• Viral infections: Norovirus¹² infection is the leading cause of diarrhea in the United States. Viral gastroenteritis can also cause watery diarrhea. Additionally, while there is a vaccine available for it, the rotavirus can also cause diarrhea.

• Bacterial infections: Numerous types of diarrhea-causing bacteria can enter the body through contaminated water and food. Campylobacter¹³, for instance (a bacteria that causes fever, stomach cramps, and diarrhea), can result from eating undercooked poultry. Campylobacter causes about 1.5 million illnesses per year.

• Parasitic infections: Intestinal parasites, such as Giardia lamblia and Entamoeba histolytica, can enter the body by drinking contaminated water or eating contaminated food and lead to diarrhea.

Many people who live with chronic diarrhea experience it as the result of an underlying digestive tract condition. Common health problems associated with chronic diarrhea include:

• Irritable bowel syndrome (IBS): A common disorder that affects the large intestine, causing abdominal cramps, gas, bloating, and diarrhea. Stress and anxiety may trigger or exacerbate IBS. Those living with the condition may be able to control symptoms by better managing their diet and lifestyle.
• Crohn’s disease: A form of inflammatory bowel disease (IBD) that causes inflammation in the digestive tract.
• Ulcerative colitis (UC): Another form of inflammatory bowel disease (IBD), UC affects the large intestine and can lead to diarrhea, inflammation in the lining of the colon, and ulcers in the digestive tract.
• Microscopic colitis: Less severe than ulcerative colitis, microscopic colitis can cause cramping and diarrhea.
• Celiac disease: Celiac disease (an immune disease in which people can’t eat gluten) can cause damage to the small intestine and result in diarrhea when foods with gluten, such as wheat, are consumed.
• Pancreatitis: Characterized by inflammation of the pancreas, both acute and chronic pancreatitis can lead to malnutrition and diarrhea.

Certain medicines can also cause diarrhea. In fact, chronic diarrhea is one of the most frequent adverse events of medication use, accounting for 7% of cases of side effects from medication. More than 700 drugs¹⁴ are known to cause diarrhea.

Some drugs commonly associated with chronic diarrhea include:

• Antibiotics, which alter the gut microbiome
• Laxatives, which are meant to cause diarrhea
• Antacids with magnesium
• Chemotherapy medicines
• Medications that suppress the immune system (called immunosuppressants), often prescribed to prevent the rejection of transplanted organs or tissues
• Pain relievers called non-steroidal anti-inflammatory drugs (NSAIDs), including ibuprofen (generic Advil, Motrin IB)

Another cause of both acute and persistent diarrhea includes food allergies and intolerances. For example, many people with lactose intolerance experience cramps and diarrhea after eating foods high in lactose, such as cheese.

Some food allergies and intolerances that can cause diarrhea include:

• Allergies to soy, seafood, cereal grains, and eggs
• Lactose intolerance (the inability to fully digest the sugars in milk)
• Fructose intolerance (the inability to properly break down fructose)
• Intolerance to sugar alcohols, such as sorbitol and xylitol (commonly found in sugar-free gum and candies)

Traveler’s diarrhea¹⁵, which is caused by drinking contaminated water or eating contaminated food, can occur when you visit a place in which the sanitation practices or climate differ from those where you live. Researchers estimate that 20–50% of travelers¹⁶ that visit developing countries experience traveler’s diarrhea. Fever or bloody stools occur in 10–20% of cases of this illness. For the most part, however, traveler’s diarrhea passes in a few days without the need for treatment.

Diarrhea may also occur as a side effect of abdominal surgery. Diarrhea following abdominal surgery may be caused by bacterial overgrowth¹⁷, poor nutrient absorption (caused by removing the intestines), and an increase in bile (common with surgeries involving the liver and gallbladder).

Your diet and lifestyle can also contribute to diarrhea. In particular, consuming alcohol¹⁸ can cause you to have diarrhea the following day. It has been proposed that excessive drinking may trigger irritable bowel syndrome (IBS)¹⁹, but more research is needed to confirm this. Caffeine²⁰ can also have a laxative effect and aggravate the symptoms of diarrhea.

Diarrhea in pregnancy

Numerous physiological changes occur during pregnancy, leading to a variety of symptoms. Both constipation and diarrhea during pregnancy are common, occurring in roughly one-third of pregnant women²¹.

Constipation during pregnancy is usually caused by hormonal changes and their effects on the digestive system. The changes in gastrointestinal motility that occur can lead to infrequent bowel movements, difficulty passing stools, and hard stools.

Diarrhea during pregnancy is often caused by the same disorders and conditions that cause diarrhea in nonpregnant people. Pregnant women usually experience diarrhea as the result of eating contaminated food, having additional stress, and taking certain medicines. Some women, however, may also become sensitive to certain foods during pregnancy, which may lead to diarrhea.

While diarrhea can occur at any time during pregnancy, it’s particularly common during the third trimester (especially when nearing the baby’s due date). Diarrhea can be a sign that you’re nearing labor. If you have diarrhea during your third trimester, however, understand that this doesn’t necessarily mean that your baby is immediately on the way. Rather, it’s a sign that your body is preparing for labor—it could be a few days (or even weeks) before labor begins²².

Most women don’t need to seek treatment for diarrhea during pregnancy. Medical experts generally advise staying hydrated by drinking plenty of water in order to prevent becoming dehydrated. Dehydration, while not always a cause for concern, can become fatal if left unaddressed for too long. Drinking beverages rich in electrolytes can also help to replenish those lost through diarrhea, while consuming broth can help replenish lost sodium.

Those traveling during pregnancy can take steps to prevent traveler’s diarrhea. Common precautions to take include avoiding “street food” and tap water (including ice), staying away from areas with inadequate sanitation, and only eating fruits that you’ve peeled yourself.

If diarrhea during pregnancy doesn’t clear up within a few days, contact your healthcare provider. They will be able to determine the cause of your symptoms and administer the proper treatment, be it antibiotics, antiparasitic drugs, or an anti-diarrheal medication like loperamide (generic Imodium).

Risk factors for diarrhea

Certain factors may increase your risk of experiencing diarrhea. Some of these factors can be managed, such as with lactose intolerance (you can help prevent diarrhea by avoiding foods and beverages containing lactose). Others, however, are the result of chronic conditions (such as ulcerative colitis) and may not be possible to prevent.

Some common risk factors for diarrhea include:

• Diet: Diet is a leading risk factor for diarrhea. Both bacterial and parasitic infections (which can come from contaminated food and water) and food sensitivities (such as lactose intolerance and food allergies) can cause diarrhea.
• Hygiene: A large medical study²³ found that frequent handwashing can help reduce diarrheal episodes by about 30%. Therefore, not maintaining proper personal hygiene may make you more susceptible to experiencing diarrhea.

• Viral infection: Certain viruses can cause diarrhea, among other symptoms. Some viral infections known to result in diarrhea include influenza, norovirus, rotavirus, and COVID-19²⁴.

• Certain medications: Non-steroidal anti-inflammatory drugs (NSAIDs), antacids containing magnesium, laxatives, chemotherapy drugs, antibiotics, and immunosuppressants have all been known to cause diarrhea as a side effect.
• Digestive conditions: People living with conditions that affect the digestive tract, such as inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), are more susceptible to experiencing both acute and chronic diarrhea.
• Lifestyle: High levels of stress and anxiety²⁵ can trigger or aggravate symptoms of IBS, as can excessive alcohol consumption.

• Traveling outside the country: Traveler’s diarrhea is common for travelers—especially those that visit developing countries.

Diarrhea symptoms

The most common symptoms of diarrhea include cramping, abdominal pain, nausea, an urgent need to use the bathroom, and, in some cases, the loss of control of bowel movements. For people with diarrhea caused by an infection, other common symptoms include fever, lightheadedness, dizziness, vomiting, and bloody stools.

More serious cases of diarrhea may lead to malabsorption, dehydration, and electrolyte imbalance. If left untreated, dehydration can lead to life-threatening problems, such as kidney failure.

Diarrhea can become dangerous—and even deadly—if severe dehydration occurs. Common signs of dehydration from diarrhea²⁶ include:

• Fatigue
• Thirst
• Less frequent urination than usual
• Dark-colored urine
• Dry mouth
• Sunken cheeks and eyes
• Decreased skin turgor (elasticity)

Infants, toddlers, and young children who are dehydrated may not produce tears while crying. Dehydrated infants may also develop a sunken soft spot on their skull.

Signs of malabsorption caused by diarrhea can include:

• Bloating
• Gas
• Weight loss
• Appetite changes
• Foul-smelling bowel movements

Experts recommend that adults with diarrhea seek medical treatment if they have symptoms of diarrhea for more than two days. In addition to watery stools, symptoms of severe diarrhea may include:

• A high fever (higher than 102°F/39°C)
• Frequent vomiting
• Severe abdominal or rectal pain
• Bloody or tarry stools
• Signs of profound dehydration
• 6 or more stools per day

Experts recommend that infants, toddlers, and young children receive medical treatment for diarrhea if their symptoms last for more than 24 hours. In addition to watery stools, symptoms of severe diarrhea in children may include:

• A high fever (higher than 102°F/39°C)
• Frequent vomiting
• Severe abdominal or rectal pain
• Bloody or tarry stools
• Signs of profound dehydration
• 6 or more stools per day

Complications from diarrhea

Young children and the elderly are at the highest risk of experiencing serious complications from diarrhea. The most severe complications from diarrhea²⁷ are those caused by dehydration and malabsorption.

Profound dehydration is the most likely to occur as the result of diarrhea in infants, toddlers, and young children. Mild dehydration generally will not cause any long-term damage. However, moderate or severe dehydration can put excess stress on the heart, lungs, and other organs. The most severe cases of dehydration can lead to shock, kidney failure, and even death.

Staying hydrated and replenishing your electrolytes helps reduce the possibility of diarrhea-induced dehydration.

Malabsorption²⁸, which affects the body’s ability to take in nutrients, is another potential complication of diarrhea. Malabsorption can cause malnutrition and weight loss and can eventually lead to other health issues, if left untreated.

If the symptoms of diarrhea persist for more than a few days, see your healthcare provider to prevent your condition from worsening or from developing complications. Your healthcare provider can provide a diagnosis for the cause of your diarrhea and determine the best course of treatment.