Get the Brief
ExplainerGut

Is IBS an Inflammatory Bowel Disease? How It Differs From IBD

IBS and IBD sound alike and can feel alike. Is IBS an inflammatory bowel disease? No. But the research finds quiet immune changes in the gut of many people with IBS.

By inflammation.news Research Desk
· 7 min read · 11 sourcesEvidence: Moderate
Four adults of different ages chat around a kitchen island as one tosses a big wooden bowl of salad beside trays of vegetable-topped toasts.“IBS Is an Inflammatory Disease”Evidence: Moderate
Illustrative photo · Askar Abayev / Pexels

The 30-second version

85.8%

of people with IBD were picked up by a stool test for calprotectin, across 17 studies.

Source 6
14.5%

of adults who had a bout of acute gastroenteritis went on to develop IBS, across 47 studies.

Source 8
820

patients in 8 trials tested an anti-inflammatory drug for IBS. It helped overall symptoms modestly, not belly pain.

Source 10
Share
The short answer

No. IBS is not an inflammatory bowel disease. Doctors now class it as a disorder of gut-brain interaction. But it is not free of inflammation either. Studies find more immune cells in the gut and higher inflammation signals in the blood of people with IBS, at levels well below those seen in IBD.

Is IBS an inflammatory bowel disease?

Two names, one letter apart. IBS stands for irritable bowel syndrome. IBD stands for inflammatory bowel disease, the group that includes Crohn's disease and ulcerative colitis. Both can bring belly pain and changes in bowel habits, and their symptoms often overlap.

But they are different conditions. In 2021, the British Society of Gastroenterology wrote that IBS had been moved into a new group: a disorder of gut-brain interaction, rather than a "functional" gut disorder. The new label came from years of research into how complex IBS is.

Doctors also reach the diagnosis in a different way. There is still no clear lab marker for IBS. A person's symptoms, and ruling out other gut diseases, are the main tools. The American College of Gastroenterology's 2021 guideline suggests making a positive diagnosis from the symptoms, rather than ruling out everything else first.

How doctors tell IBS and IBD apart

The guideline suggests one stool test for people with suspected IBS and diarrhea: fecal calprotectin, used to rule out IBD. It also suggests a blood test for celiac disease.

Calprotectin is higher in people with IBS than in healthy people, yet still well below the levels in IBD.From a 2026 meta-analysis in EBioMedicine

How good is the stool test? A 2023 meta-analysis pooled 17 studies with 1,956 patients. A meta-analysis combines the results of many studies. The test caught 85.8% of people who had IBD and correctly cleared 91.7% of people with IBS. When only 1 in 100 people tested has IBD, a negative result was right 99.8% of the time. One caution: the review judged every study at high or unclear risk of bias.

The overlap runs the other way too. A 2020 meta-analysis of 27 studies looked at 3,169 people whose IBD was in remission. About 1 in 3 still had symptoms that fit IBS. Even when a scope showed the gut had healed, about a quarter did. Those symptoms went along with higher anxiety and depression scores.

What is going on in the gut lining?

Here is where the simple "no" gets more interesting. A 2018 meta-analysis compared colon samples from 706 people with IBS and 401 people without it, across 22 studies. The IBS group had more mast cells and more T cells, two kinds of immune cells. The change showed up in people whose IBS leans toward constipation and in those whose IBS leans toward diarrhea. It also varied by section of the colon.

A 2019 review of 51 papers found the same kind of picture, with changes in several types of immune cells. Its authors called the immune activity "subtle." They also noted that studies are hard to compare, because IBS looks different from one person to the next.

Subtle is the key word. Calprotectin is higher in people with IBS than in healthy people. Yet it is still well below the levels in people with IBD and similar gut diseases.

When a stomach bug comes first

Some of the best clues come from people who got sick first. A 2024 meta-analysis of 47 studies followed adults after a bout of acute gastroenteritis, the stomach bug kind of infection. In all, 14.5% went on to develop IBS. People who had the infection had 4.3 times the odds of IBS compared with people who did not. And IBS was still there in 39.8% of them more than 5 years later.

A Rome Foundation team report calls this post-infection IBS. It points to changes in gut bacteria and in the gut lining, plus serotonin and immune factors. The same report says these steps are not fully understood, and that no drug has been proven to treat this form of IBS.

Can anti-inflammatory treatment help IBS?

If inflammation drove all IBS, an anti-inflammatory drug should help a lot. Researchers have tested that idea with mesalamine, a drug with anti-inflammatory effects. A 2024 meta-analysis of 8 randomized trials with 820 patients found a modest effect: about 10 people had to take it for 1 more to feel better overall. Belly pain and bowel habits did not budge. The evidence was rated low quality.

That result fits the rest of the research. Inflammation looks like one part of IBS for some people, not the whole story.

What this means for you

Tick what you'll try this week. Your picks stay on this device.

Talk to your doctor first if

you see blood in your stool, lose weight without trying, have a fever, wake at night with diarrhea, notice symptoms that started after age 50, or have a family history of IBD or colon cancer. Check in before any strict diet if you have had an eating disorder or are at risk of poor nutrition.

Will you try it?

One tap. Results appear once 50 readers have voted, and the count is always real.

The bottom line

The two names sit one letter apart, and the gap between them is real. IBD is, by name and by nature, an inflammatory disease. IBS is a disorder of how the gut and brain work together. Yet the colon samples, the blood tests and the stomach bugs all point the same way: in many people with IBS, the immune system is a little more awake than it should be. A little, not a lot. So the useful first step is the plain one: rule out IBD, then work on the symptoms with tools that have been tested.

Common questions

Does IBS cause inflammation in the body?

Somewhat, on average. A 2026 meta-analysis of 124 studies, with 14,930 people with IBS, found higher levels of TNF-alpha and IL-6 in their blood than in healthy people. These are signaling proteins that help drive inflammation. Results varied a lot between studies, and the authors say there is still no clear blood marker for IBS.

Does IBS cause inflammation in the colon?

Mildly, in many people. Across 22 studies, colon samples from people with IBS held more mast cells and T cells, two kinds of immune cells, than samples from people without IBS. But stool calprotectin, a marker of gut inflammation, stays well below the levels seen in IBD.

Is there an anti-inflammatory diet for IBS?

Not one with proof behind it as an anti-inflammatory treatment. The diet with the most evidence for IBS symptoms is the low-FODMAP diet, used for a short time and then loosened. The American College of Gastroenterology recommends a limited trial of it. Soluble fiber also helps overall symptoms.

Can you have IBS and IBD at the same time?

Symptoms can overlap. In 27 studies of 3,169 people whose IBD was in remission, about 1 in 3 had symptoms that fit IBS. Even among people whose gut looked healed on a scope, about a quarter did. Their doctors can check whether the IBD is active before treating the symptoms as IBS.

Ask the Research Desk

Heard something about inflammation you want checked? The best questions become articles, credited by first name only if you say yes.

How this article was made

Researched and written from 11 peer-reviewed papers. Our automated check matched every claim against the exact words of its source, confirmed every paper exists in PubMed, and found none retracted. Checked October 30, 2026. Not individually reviewed by a doctor. Photos are illustrative; the people in them are not patients or readers.

Grades run Strong, Moderate, Emerging, Early and Not supported, and the grade decides the words we may use. How we grade evidence · Medical disclaimer

Sources

  1. GuidelineACG Clinical Guideline: Management of Irritable Bowel Syndrome.Lacy BE, Pimentel M, Brenner DM et al. Am J Gastroenterol, 2021.PubMedFull paper
  2. GuidelineBritish Society of Gastroenterology guidelines on the management of irritable bowel syndrome.Vasant DH, Paine PA, Black CJ et al. Gut, 2021.PubMedFull paper
  3. Meta-analysisSerological and faecal markers of irritable bowel syndrome: a systematic review and meta-analysis.Burns GL, Roberts F, Wark JA et al. EBioMedicine, 2026.PubMedFull paper
  4. Meta-analysisColonic immune cells in irritable bowel syndrome: A systematic review and meta-analysis.Bashashati M, Moossavi S, Cremon C et al. Neurogastroenterol Motil, 2018.PubMedFull paper
  5. Systematic reviewEvidence for Local and Systemic Immune Activation in Functional Dyspepsia and the Irritable Bowel Syndrome: A Systematic Review.Burns G, Carroll G, Mathe A et al. Am J Gastroenterol, 2019.PubMedFull paper
  6. Meta-analysisSystematic review with meta-analysis: Diagnostic performance of faecal calprotectin in distinguishing inflammatory bowel disease from irritable bowel syndrome in adults.Dajti E, Frazzoni L, Iascone V et al. Aliment Pharmacol Ther, 2023.PubMedFull paper
  7. Meta-analysisPrevalence of irritable bowel syndrome-type symptoms in patients with inflammatory bowel disease in remission: a systematic review and meta-analysis.Fairbrass KM, Costantino SJ, Gracie DJ et al. Lancet Gastroenterol Hepatol, 2020.PubMedFull paper
  8. Meta-analysisPrevalence of irritable bowel syndrome and functional dyspepsia after acute gastroenteritis: systematic review and meta-analysis.Porcari S, Ingrosso MR, Maida M et al. Gut, 2024.PubMedFull paper
  9. Systematic reviewRome Foundation Working Team Report on Post-Infection Irritable Bowel Syndrome.Barbara G, Grover M, Bercik P et al. Gastroenterology, 2019.PubMedFull paper
  10. Meta-analysisSystematic Review and Meta-analysis: Efficacy of Mesalamine in Irritable Bowel Syndrome.Goodoory VC, Tuteja AK, Black CJ et al. Clin Gastroenterol Hepatol, 2024.PubMedFull paper
  11. ReviewAGA Clinical Practice Update on the Role of Diet in Irritable Bowel Syndrome: Expert Review.Chey WD, Hashash JG, Manning L et al. Gastroenterology, 2022.PubMedFull paper
A woman with long fair hair sits by a large sunny window with a mug of coffee, reading on her phone.
Illustrative photo · MART PRODUCTION / Pexels

Keep reading

Four adults of different ages chat around a kitchen island as one tosses a big wooden bowl of salad beside trays of vegetable-topped toasts.“Yogurt Is Inflammatory”Evidence: ModerateExplainerGut

Is Yogurt Inflammatory? What Studies on Dairy and Fermented Foods Show

Is yogurt an inflammatory food? Dozens of trials checked blood markers of inflammation after people ate yogurt and other dairy. Here is what they found, and the one group it really does inflame.

A young boy kisses his smiling grandmother on the cheek at a table set with a big bowl of salad greens, apples and bread.“Tomatoes Are Inflammatory”Evidence: Not supportedMyth CheckFood

Are Tomatoes an Inflammatory Food? What Trials Show About Nightshades

Tomatoes, peppers, eggplant and potatoes often land on lists of foods to cut for inflammation. In trials where people ate more tomato, blood signs of inflammation did not go up.

A couple chat and laugh by a sunny kitchen window, each holding a bowl of fruit, with sliced grapefruit on the counter.“Going Gluten-free Reduces Inflammation”Evidence: EmergingMyth CheckFood

Does Going Gluten-Free Reduce Inflammation? Only for Some People

For people with celiac disease, cutting gluten is the treatment. For everyone else, the studies on whether going gluten-free reduces inflammation are small, short and mixed.