Top 10 Reasons for Acute and Chronic Diarrhea

Diarrhea is an urgent problem. Peter Cade/Getty Images

Bowel movements aren’t necessarily a fun thing to talk about. In fact, the topic can be quite embarrassing. But, if you have a food allergy, the topic of bowel movements is one with which you’ll want to be familiar. Most importantly, knowing what your “norm” is when it comes frequency and consistency of bowel movements can help you interpret when things become “off.”

When it comes to bowel movements, what is "normal" is loosely defined (no pun intended) and varies from person to person, diet to diet, and age to age.

Diarrhea, though, is not normal on a day-to-day basis, and can be a symptom of an underlying condition, which may take some work to figure out. There are two types of diarrhea to consider: acute diarrhea, which starts suddenly, and chronic diarrhea, which goes on without resolution for a period of time. There are many causes of both acute and chronic diarrhea. Let’s take a look at both:

Acute Diarrhea

Acute diarrhea begins suddenly, and often without warning. The most common cause is an infection: from bacteria, a virus, or a parasite. Although there are many causes of acute diarrhea, these three are the most common reasons:

Food Poisoning

Food poisoning occurs when you eat food that has become contaminated with bacteria. Poor sanitation or food being stored at the wrong temperature may lead to bacterial contamination. It is the bacterial toxins in the food that make you sick.

  • Duration of diarrhea: Usually less than 2 days
  • Triggered by: Toxins in food
  • Symptoms appear within: 2 to 6 hours of eating contaminated food
  • Appearance of diarrhea: Explosive, watery
  • Other symptoms: Abdominal cramps, fever, vomiting, weakness, and dehydration

Traveler’s Diarrhea

Traveler’s diarrhea occurs with eating food or drinking water that has been contaminated with bacteria or parasites.

Most traveler’s diarrhea will get better with home care in a few days. If you have recently traveled to a tropical country and you have diarrhea, call your doctor.

  • Duration of diarrhea: Usually less than 1 week
  • Triggered by: Food or water that is contaminated by bacteria, viruses, or parasites
  • Symptoms appear within: 12 to 24 hours
  • Appearance of diarrhea: Explosive, watery, sometimes contains mucous or blood
  • Other symptoms: Possibly vomiting and/or fever

Stomach Flu

The stomach flu is caused by a virus and results in an infection of the stomach and intestines. This is unlike the “flu,” or influenza, that generally involves not only the gastrointestinal tract but also the respiratory tract, as well. The stomach flu can be remedied with home treatment, such as fluids. Young children, the elderly, and people with compromised immune systems are at risk for dehydration, and should be watched closely for signs of more serious complications.

  • Duration of diarrhea: Usually 3 – 8 days
  • Triggered by: A virus
  • Symptoms appear within: 2 days after exposure
  • Appearance of diarrhea: Watery
  • Other symptoms: Vomiting, fever, achiness, cramps, and possible dehydration

Chronic Diarrhea

Diarrhea that goes on for weeks or months at a time may be caused by an infection, or by an underlying medical condition. There are many causes of chronic diarrhea, however. Some of the more common reasons are listed here. If you have had diarrhea for more than three days, seek help from your doctor.

Celiac Disease

If you have untreated celiac disease, you may have a hard time linking your symptoms to a specific food because your gut is damaged and your symptoms may be present all the time.

  • Duration of diarrhea: More than 4 weeks
  • Triggered by: Gluten, which is present in all wheat-containing foods. Pinpointing symptoms to a specific meal may be difficult.
  • Appearance of diarrhea: Large, bad-smelling stools that float in the toilet water
  • Other symptoms: Unintended weight loss, lack of energy, lack of growth in children, and nutrient deficiencies, especially iron

Food Allergy

Symptoms of classic Ig-E mediated food allergy begin within minutes to hours of eating a trigger food. It is possible to be allergic to any food, but a few foods cause the most common food allergies.

  • How long diarrhea lasts: Usually less than 24 hours
  • Triggered by: A specific food
  • Symptoms appear within: 2 hours
  • Appearance: Watery, may contain blood
  • Other symptoms: Hives; vomiting; swelling of face, tongue or throat; eczema

Food Intolerance

Food intolerance is caused by a lack of the enzymes needed to digest a specific food. For example, lactose intolerance is the inability to digest the sugar called lactose in milk, and is the most common food intolerance.

  • Duration of diarrhea: More than 4 weeks
  • Triggered by: A specific food
  • Symptoms appear within: 2 to 12 hours
  • Appearance of diarrhea: Watery, sometimes contains mucous
  • Other symptoms: Gassiness, abdominal cramps or pain

Inflammatory Bowel Disease

Inflammatory bowel disease, including Crohn's disease and ulcerative colitis, have chronic diarrhea as a symptom. Both are diseases of the digestive tract that may be treated with surgery or managed with medication.

  • Duration of diarrhea: More than 4 weeks
  • Triggered by: Not related to a specific food
  • Appearance of diarrhea: Blood or mucous in stool
  • Other symptoms: Abdominal pain, fever, weight loss, slow growth in children

Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) describes a condition that includes chronic diarrhea, constipation, and abdominal pain that does not have a known disease as a cause. If you have been diagnosed with IBS, discuss the possibility of celiac disease with your doctor, as the American College of Gastroenterology recommends anyone diagnosed with IBS and diarrhea be tested for celiac disease.

  • Duration of diarrhea: At least six months
  • Triggered by: Not related to a specific food, though certain foods may aggravate symptoms
  • Appearance of diarrhea: Small, frequent stools
  • Other symptoms: Chronic abdominal bloating or distention; constipation. Pain is relieved by a bowel movement.

Milk/Soy Protein Intolerance

Infants may show signs of protein intolerance within a few months of birth. Infants may react to food proteins present in breast milk, while others may react to formulas made with either cow’s milk or soy.

  • Duration of diarrhea: More than two weeks
  • Triggered by: Dairy or soy products; sometimes caused by egg or other food proteins
  • Symptoms appear within: 2 hours or more
  • Appearance of diarrhea: Streaks of mucous or blood
  • Other symptoms: Distended belly, crying, failure to gain weight and grow, also called Failure to Thrive (FTT).


Some medications, such as antibiotics and chemotherapy, may cause diarrhea due to the medication itself or an additive, such as a flavoring. Medication may also alter the balance of bacteria in your gut, causing abdominal pain and diarrhea. Talk to your doctor if you have diarrhea after starting a new medication.

What Your Doctor Will Ask About Your Diarrhea

In order to figure out the cause of your diarrhea, your doctor is likely to ask you these questions:

How long have you had diarrhea? While not an absolute rule, diarrhea that started suddenly in the last 24 hours may indicate an infection or virus. If it has been going on for months or years, you may have a food intolerance or inflammatory bowel disease.

When did it begin? You doctor will want to know if you were traveling out of the country recently or if you ate any foods you suspect are causing your diarrhea. Food allergy symptoms begin immediately after eating a food, while diarrhea caused by intolerances or infections may be delayed by 12 hours or more.

How many stools a day are you having? Normal stool frequency is between 2-3 per day and 2-3 per week. Three or more unformed stools a day indicates diarrhea.

What does it look like? Diarrhea may include loose, watery, mucous-containing, or dark-colored stools. Black or bright red diarrhea may mean there is blood in your stool, which is a serious condition that needs immediate medical care.

Treatment for Diarrhea

You can care for most diarrhea using at-home treatments, such as drinking plenty of fluids and eating mild foods until the diarrhea resolves and you are able to transition back to a normal diet, however some symptoms need immediate medical care.


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