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Why does diarrhea hurt so much?

Diarrhea can be an uncomfortable and painful experience. The abdominal cramps and urge to have frequent bowel movements can disrupt daily life. But why does diarrhea cause such discomfort? There are a few key reasons why diarrhea is often accompanied by abdominal pain.

Increased Motility in the Intestines

One of the hallmark symptoms of diarrhea is an increase in the motility or contractions of the muscles in the intestines. Normally, the intestines contract in a coordinated pattern called peristalsis which slowly moves food through the digestive tract. In diarrhea, the contractions become much stronger and faster.

This increase in motility is the intestines attempt to quickly expel the excess water and electrolytes lost during diarrhea. But these strong and frequent contractions can stimulate the nerves in the intestines, causing abdominal cramps and discomfort.


Many cases of diarrhea are caused by inflammation in the intestines. Inflammation can occur from bacterial, viral, or parasitic infections. Inflammatory bowel diseases like Crohn’s disease or ulcerative colitis can also lead to diarrhea.

The inflamed intestines become irritated and sensitive. The excess motor activity during diarrhea can rub against the inflamed areas, causing pain and discomfort. The intestines may also leak small amounts of mucus and fluid which can stimulate the intestinal nerves and result in cramps.

Loss of Water and Electrolytes

Diarrhea causes significant losses of water and important electrolytes like sodium, potassium, and chloride. Adults can lose up to 3 liters of fluid per day with severe diarrhea. Losing these essential electrolytes causes the muscles – including those in the intestines – to contract abnormally and go into spasms, leading to cramps.

The water loss from diarrhea also makes the stools firmer and drier. This can exacerbate irritation and inflammation as these hard stools pass through the intestines. The loss of water from the body also leads to dehydration, which can make any muscle cramping feel more intense.

Irritation of the Rectum

As the excess liquid stool from diarrhea reaches the rectum, the nerves in the rectum and anus can become irritated. This can cause a painful and urgent feeling of needing to have a bowel movement. Frequent wiping after loose stools can further aggravate the irritated rectal area.

Over time, the rectal nerves can go into overdrive, becoming hypersensitive. Even once the diarrhea resolves it may continue to feel like you constantly need to have a bowel movement. This condition is called tenesmus.


Some medications used to treat diarrhea can actually make the cramping worse, at least temporarily. Loperamide or Imodium works by slowing down motility in the intestines. But before it kicks in, it may cause the intestines to contract more vigorously which can increase cramping.

Other anti-diarrheal medications like diphenoxylate with atropine work directly on the nerves in the intestine to reduce muscle contractions. So these may actually provide some relief from the painful cramps that occur with diarrhea.

Who is Most at Risk for Painful Diarrhea?

While anyone can get abdominal cramps from diarrhea, some groups seem to be more prone to painful diarrhea episodes:

  • Young children – They have lower tolerance for the fluid shifts and electrolyte abnormalities with diarrhea.
  • Older adults – They may have weaker intestinal muscles that are more prone to spasms. The nerves in their intestines may also be more sensitive.
  • People with inflammatory bowel disease – They often have chronic intestinal inflammation that can be aggravated.
  • Females – Hormonal fluctuations may make the nerves in their intestines more sensitive.
  • People who have had gastrointestinal surgery – Scarring and adhesions can make the intestines less coordinated.
  • Individuals with anxious personalities – They may have increased sensitivity to physical discomfort.

Treatments to Reduce Diarrhea Pain

While mild cases may resolve on their own, there are some treatments that can help reduce the abdominal discomfort that often accompanies diarrhea:

  • Over-the-counter anti-diarrheals – Medications like loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol) can help slow intestinal contractions.
  • Prescription anti-spasmodics – These directly relax the intestinal muscles to reduce spasms and cramps.
  • Low FODMAP diet – Avoiding foods that ferment in the colon can reduce irritation.
  • Probiotics – Friendly bacteria like yogurt can help restore normal intestinal function.
  • Peppermint oil – It has anti-spasmodic effects on intestinal muscles.
  • Gentle massage – Light pressure on the abdomen can relieve gas buildup.
  • Heating pads – Applied to the lower abdomen, heat can ease muscle tension.

It’s also critical to stay hydrated by drinking fluids like diluted fruit juices, coconut water, or oral rehydration solutions. Preventing dehydration can help reduce painful muscle cramps both during and after diarrhea.

When to See a Doctor

Mild abdominal discomfort from diarrhea will often resolve within 48 hours as your stools return to normal. But see a doctor right away if you have:

  • Diarrhea lasting more than 2 days
  • Bloody or black stools
  • Severe pain that worsens or spreads
  • Fever over 101 F (38 C)
  • Signs of dehydration like dizziness or rapid heart rate

This could indicate a serious condition like appendicitis, bowel obstruction, or intestinal infection that requires treatment. Severe dehydration from ongoing diarrhea can become life-threatening.

When Diarrhea Pain May Indicate IBS

For some people, abdominal pain from diarrhea comes and goes randomly. It may happen more during stressful life events. The pain and diarrhea can alternate with periods of constipation.

This pattern is common for those with irritable bowel syndrome or IBS. It’s a chronic condition affecting the large intestine that can cause uncomfortable digestive symptoms. IBS is often diagnosed when:

  • Diarrhea and pain persist weeks after an infection has cleared
  • Symptoms are triggered by certain foods like dairy, greasy foods, beans, etc.
  • Diarrhea is associated with bloating, gas, cramping, and constipation
  • Symptoms began after a major life stress or event

IBS is managed through diet changes, stress management, and medications to control diarrhea and pain. Identifying and avoiding your personal trigger foods is key.

Can Probiotics Help Diarrhea Pain?

Probiotics have become a popular supplement for digestive issues like diarrhea. They contain beneficial bacteria that can help restore balance to the intestines after an infection or episode of diarrhea. Some of the ways probiotics may help with diarrhea pain include:

  • Reducing inflammatory cytokines that irritate the intestines
  • Increasing mucus production which acts as a barrier against irritation
  • Blocking harmful bacteria like Salmonella or E. coli from attaching to the intestinal walls
  • Replenishing electrolytes like sodium and potassium
  • Lessening muscle hypercontractility

Studies have found some strains like Lactobacillus rhamnosus GG and Saccharomyces boulardii CNCM I-745 can help shorten the duration of diarrhea in children and adults by 1-2 days. They may also reduce the number of stools and need for IV rehydration.

Probiotics are considered very safe since they contain natural gut bacteria. They can be taken preventatively and during diarrhea episodes. But ask your doctor before use if you have a weakened immune system.

Probiotic Strain CFU Count Evidence for Diarrhea
Lactobacillus rhamnosus GG 10 billion Clinical trials show it shortens duration of diarrhea in kids and adults by ~2 days.
Saccharomyces boulardii CNCM I-745 250 mg Meta-analyses find it reduces risk of antibiotic-associated diarrhea by 52-62%.
Lactobacillus acidophilus 2-10 billion May reduce diarrhea from irritable bowel syndrome according to some studies.

Lifestyle Changes to Prevent Diarrhea Discomfort

Making some diet and lifestyle adjustments can help decrease episodes of painful diarrhea:

  • Drink 8-10 glasses of fluids daily
  • Avoid dairy if you’re lactose intolerant
  • Limit greasy, fried, and spicy foods
  • Reduce alcohol and caffeine intake
  • Stop smoking cigarettes
  • Prevent foodborne illness by washing produce and cooking meat thoroughly
  • Wash hands frequently, especially before eating
  • Learn healthy ways to manage stress and anxiety

No one enjoys dealing with diarrhea and abdominal discomfort. But understanding what causes the pain along with treatments can help you get relief faster and prevent episodes in the future.

The Bottom Line

Diarrhea often causes painful abdominal cramps due to increased contractions in the intestines, inflammation, electrolyte imbalances, and rectal irritation. Staying hydrated and taking over-the-counter or prescription anti-diarrheals can help manage discomfort. Seek medical care for severe pain, bloody stools, fever, or dehydration. Lifestyle adjustments like probiotic use, a low FODMAP diet, and stress management may prevent recurrences.