Constant Diarrhea & Abdominal Pain: 8 Causes Simplified.

Our content is not intended nor recommended as a substitute for medical advice by your doctor. Use for informational purposes only.

What you need to know:

  • The term (constant diarrhea) may refer to a short-term attack of (constant acute diarrhea) or a prolonged (chronic constant diarrhea).
  • The causes of acute constant diarrhea and abdominal pain are often infections such as viral gastroenteritis, and foodborne illness (food poisoning).
  • Chronic constant diarrhea and abdominal pain can occur due to a variety of conditions such as food intolerance, IBD, celiac diseases, IBS, and others.
  • See a doctor if you have severe symptoms, with dehydration, fever, or blood in the stool.

1 . Infections (gastroenteritis):

A- Viral Gastroenteritis (stomach flu).

Viral gastroenteritis (stomach flu) is the most common cause of acute infectious diarrhea (in about 60%) (reference).

The symptoms typically are:

  • Acute onset diarrhea (usually water, and yellowish or bright yellow in color).
  • Stomach (abdominal) cramps.
  • Nausea and maybe vomiting.
  • Sometimes, Gas and bloating occur.
  • Low-grade fever.
  • It usually lasts for one to 4 days. But diarrhea may become constant for a week or two.

common infections causing bright yellow watery diarrhea

Image Data Reference

B- Other infections and food-borne illnesses.

Other infections that can cause acute attacks of constant diarrhea and gas include:

  • Bacterial infections (The non-inflammatory type).
    Bacterial diarrhea usually causes a severe form of bloody mucus diarrhea with high-grade fever (inflammatory diarrhea).
    However, milder forms of bacterial diarrhea (non-inflammatory) can cause constant diarrhea and gas.
  • Protozoal infections (especially giardiasis).
    Giardiasis is the most common type of protozoal infection (reference: CDC). It is caused by ingesting contaminated foods or drinks.
    Giardiasis can cause a severe form of foul-smelling, yellowish, and constant diarrhea for days or weeks.
    It also causes fat malabsorption, resulting in yellowish constant diarrhea and gas.

2. Food intolerance and allergy.

Intolerance or allergy to certain foods or drinks is a widespread condition. It is estimated that up to 20% of people have some form of food intolerance.

Lactose is a sugar present in milk and other dairy products. Lactose intolerance is shockingly common among some races.

The prevalence of lactose intolerance in the white population is about 20%, and it may go up to 90% in certain other races (reference).

Lactose intolerance is just one example of food intolerance. a long list of foods and drinks can cause food intolerance or food allergy.

Common types of food intolerance and allergy:

  • Lactose intolerance: Present in milk, ice cream, mustard, some types of cheese.
  • Fructose intolerance: Present in many fruits and honey.
  • FODMAPs intolerance: It affects people with IBS. FODMAPs refer to “Fermentable Oligo-, Di-, Monosaccharides, and Polyols. FODMAPs are a group of short-chain carbohydrates that cause gas and digestive disturbances. They are present in a wide variety of foods, vegetables, fruits, and artificial sweeteners. Learn more.
  • Caffeine intolerance: Caffeine in coffee, teas, and chocolates is one of the most common causes of constant diarrhea. Caffeine is usually abused in large amounts which raises the risk of diarrhea.
  • Alochol intolerance: Too much drinking causes diarrhea and some of them are high in FODMAPs and can trigger IBS symptoms.
  • Gluten intolerance:
    It causes Celiac disease (see later) and another milder form called “Non-celiac gluten sensitivity”.
  • Amines intolerance:
    Amines are produced by bacteria during food storage and fermentation.
  • Salicylates intolerance: Salicylates are naturally occurring chemicals. They present in a wide variety of foods including fruits, vegetables, coffee, and teas.
  • Sulfite intolerance: Sulfite is used as a natural preservative for foods.
  • Food allergy: Some foods can cause more severe allergic reactions such as Nuts, peanuts, raw meat, seafood, mustard, rice, and some fruits and vegetables.

The difference between food intolerances and food allergies is described in the table below:

Food intolerance

Food allergy

Affects 15-20% of the populationAffects nearly 2-5% of adults
Difficulty digesting certain types of food (not immune-mediated allergy).An immune-mediated reaction to certain foods or food components.
Can cause “constant” or “chronic” attacks of diarrhea.Usually causes acute attacks or is related to the ingestion of offending food.
Intestinal symptoms: diarrhea, extensive gas, bloating, and abdominal painIntestinal symptoms are the same
No extra-intestinal symptomsExtra-intestinal symptoms like rashes, urticaria, swollen lips or face, or severe life-threatening allergic reactions.
The severity of your symptoms is proportional to the amount you eat from the offending food.Even trace amounts of the offending food can produce severe symptoms.

Common offending foods:

  • Lactose intolerance (dairy products).
  • Fructose malabsorption.
  • Alochol intolerance.
  • FODMAP intolerance (as with People with IBS).

Common offending foods: (examples)

  • Raw meat, seafood.
  • Nuts, peanut
  • Mustard.
  • Rice
  • Some vegetables and fruits.

3. Irritable bowel syndrome with diarrhea (IBS-D).

Irritable bowel syndrome affects too many people worldwide. Approximately 10 to 15% of people have IBS (reference).

Surprisingly, Too many people who match the criteria of IBS don’t seek medical advice. Some studies estimated that 60% of people with IBS symptoms don’t know they have the disease! (reference).

IBS has 4 subtypes according to the predominant symptom. What concerns us today is the diarrhea-predominant IBS. Diarrhea-predominant IBS is one of the most common causes of constant diarrhea.

Symptoms (how to suspect IBS-diarrhea):

  • Abdominal pain: is the fundamental symptom of IBS. IBS sufferers experience abdominal pain at least one day per week for the past 3 months.
  • The abdominal pain either improves or worsens after the bowel movement.
  • The onset of abdominal pain is associated with diarrhea and loose stool (change in stool form).
  • Bloating is frequent in people with IBS.
  • Intermittent or constant diarrhea.
  • Mucus in the stool.

The IBS is usually triggered by:

  • Certain foods such as FODMAPs.
  • alocholoand caffeine.
  • Fatty foods and spicy foods.
  • Stress and anxiety.

The following symptoms are NOT among IBS symptoms:

  • Abdominal pain awakens you at night.
  • Fever.
  • Blood in stool.
  • Weight loss.
  • Vomiting.
  • Anemia.

IBS is a functional bowel disease. This means we couldn’t find specific lesions by investigation. IBS can only be diagnosed by a doctor after the exclusion of other organic diseases.

The ROME IV criteria are the most accepted method for diagnosing IBS. The ROME IV symptom-based criteria. Until now, No specific imaging or lab test can diagnose IBS.

If you suspect IBS is a cause of constant diarrhea. Learn how is IBS diagnosed in this in-depth article.

Arrange a visit to your doctor to get diagnosed.

4. Celiac disease.

Celiac disease is an extreme form of food intolerance. It is a common disease affecting 1% of the world population.

With celiac disease, your body is intolerant to a protein called “gluten”. Gluten is found mainly in:

  • Wheat and wheat-based foods such as bread.
  • Rye.
  • Barley.

A small intestinal inflammation with malabsorption develops after eating gluten-containing foods. Celiac disease can cause constant diarrhea for years if people don’t seek medical advice.

Symptoms suggesting celiac disease:

  • The usual age of onset is between 20-30 years of age. But it can occur in older ages up to 70 years.
  • Abdominal pain and bloating.
  • Constant diarrhea.
  • Diarrhea can also be intermittent or not present. Constipation can also occur.
  • Nausea and vomiting.
  • Weight loss.
  • Easy fatigue and iron deficiency anemia.
  • Itchy, blistery skin.
  • Osteoporosis and osteomalacia (body aches).

Celiac disease is diagnosed by a blood test or by taking a biopsy from the small intestine.

Call your doctor if you suspect celiac disease. Learn more.

5. Medication-induced diarrhea.

Vague constant diarrhea for long periods can be a result of medications you take. Diarrhea is a documented side effect of more than 700 medications (reference).

Common medications that can cause constant  diarrhea:

  • Antibiotics: Any type of antibiotic can kill the beneficial bacteria inside your colon.
  • Some anti-diabetes medications: Metformin and gliptins (vildagliptin, sitagliptin, and others) can cause diarrhea and stomach gurgling.
  • Laxative overuse.
  • Stomach/GERD medications: PPIs (as omeprazole, esomeprazole, and pantoprazole) and H2 blocker inhibit stomach acid. This inhibition will allow for the overgrowth of bacteria inside the small intestine and colon causing stomach gurgling and diarrhea.
  • Others such as chemotherapy, immunosuppressive medications can also cause such conditions.

The complete list of medications causing diarrhea is HERE and HERE.

6. Inflammatory bowel disease.

Inflammatory bowel disease refers to 2 major conditions:

  • Crohn’s disease: Unexplained inflammation and ulceration at any part of your gut (from the mouth to the anorectum).
  • Ulcerative colitis: Unexplained inflammation and ulceration affecting the large intestine only (the colon and the retcum).

About 1.8 million U.S adults (0.9%) had inflammatory bowel disease according to the CDC.

symptoms of IBD:

  • Persistent or recurrent diarrhea.
  • Abdominal pain.
  • Blood or blood and mucus coming out with or without a stool.
  • Weight loss.
  • Generalized fatigue.
  • Fever may occur.
  • Loss of appetite.

Suspect IBD if you have a prolonged history of abdominal pain, mucus, constant diarrhea, and blood in stool without obvious cause.

The main differences between Crohn’s and ulcerative colitis are summarized in the below table.

TypeCrohn’s DiseaseUlcerative Colitis
1- SiteAny part of the GI tract (from the mouth to the anorectum)The colon and retcum.
2- LesionsDeeper, it can involve all the layers of the GI wall.Usually superficial (only in the innermost layer)
3-Predominant symptomCrampy abdominal painBloody diarrhea. (can be constant)
4- ComplicationsFistulas, abscess, intestinal obstructionhemorrhagic toxic megacolon.
5- Risk of colon cancerSlight increaseMarked increase

Ulcerative colitis and Crohn’s disease are major diseases that require medical care and follow-up.

If you have a long history of recurrent abdominal pain, constant diarrhea with blood, and mucus in stool, consult your doctor.

7. Bile acid diarrhea.

Bile acid diarrhea (BAD) is one of the most underrated causes of chronic and constant diarrhea in medicine.

Normally, your small intestine reabsorbs more than 95% of bile excreted from the liver through the gallbladder and bile duct (reference).

Excess bile acid secretion or malabsorption of the bile acid leads to Bile acid diarrhea.

How common is bile acid diarrhea?

Bile acid diarrhea is more common than you think. And it is often misdiagnosed as IBS-D

The following facts and statistics will help you imagine the amplitude of BAD:

  • About 25 to 50% of patients diagnosed with IBS-diarrhea actually have BAD (reference).
  • It is estimated that about 1% of the population may have BAD.
  • It is estimated that about 64% of patients with Functional diarrhea have BAD (reference).
  • Up to 35% of people with a condition called “microscopic colitis” have BAD (reference).

Symptoms suggestive of Bile acid diarrhea:

  • Constant diarrhea (especially after fatty meals).
  • Extreme urgency: a sudden severe urge to poop.
  • The extreme urgency may lead to soiling accidents (stool incontinence) in some people.
  • Unlike IBS, diarrhea can occur at night (awakens you from sleep).
  • Abdominal pain and stomach gurgling after meals.
  • Bloating and flatulence.

Bile acid is overlooked by many doctors. This is due to the relative unavailability of its specific test (SeHCAT test) and the similarity of symptoms with IBS.

The treatment of bile acid diarrhea is a bile acid binder called cholestyramine (Questran). We discussed the issue of BAD and its relation to IBS-D  in-depth HERE.

8. Others (less frequent):

Too many diseases and conditions can lead to constant diarrhea and abdominal pain. The above 7 causes are the most frequent.

Other less common causes include:

  • Colon cancer
  • Small intestinal bacterial overgrowth (SIBO)
  • Gastrointestinal lymphoma.
  • Chronic pancreatitis.
  • Pancreatic cancer.
  • Hyperactive thyroid gland (hyperthyroidism).
  • Radiation (used for cancer treatment).
  • Diabetes Mellitus.
  • Cystic fibrosis.
  • Whipple’s disease and tropical sprue.
  • Hyperparathyroidism
  • Addison’s disease.
  • Hormone secreting neuroendocrine tumors such as carcinoid, gastrinoma, and VIPoma).
  • Autonomic neuropathy.

MORE: Indigestion & Diarrhea: 9 Common Causes (Acute & Chronic).