Rahway, N.J. – September 23, 2026 -- Patients dealing with prolonged diarrhea and abdominal pain often confuse inflammatory bowel disease (IBD) with irritable bowel syndrome (IBS), despite the two being fundamentally different conditions, according to a new editorial from MerckManuals.com by Dr. Aaron E. Walfish of Mount Sinai Medical Center.

IBD causes physical damage that IBS does not

Walfish explains that IBS is a functional disorder where the digestive tract looks normal but doesn't work properly. IBD, by contrast, involves chronic inflammation that shows up on a colonoscopy, imaging, or biopsy. Left untreated, IBD can lead to fistulas, abscesses, undernutrition, and a higher risk of colorectal cancer. Because it's a systemic disease, it can also trigger joint pain, eye inflammation, skin issues, and fatigue elsewhere in the body.

Crohn disease and ulcerative colitis are the two main forms

Crohn disease typically inflames the lower small intestine, the large intestine, or both, though it can affect any part of the digestive tract. Ulcerative colitis mainly targets the colon, causing ulceration that often leads to bloody diarrhea, cramps, and fever.

No cure exists, but treatment has improved significantly

Doctors still don't know exactly what causes IBD. Evidence points to normal gut bacteria triggering an inappropriate immune response in people with a genetic predisposition, with smoking identified as an additional risk factor. Walfish notes that while there's no cure, treatments developed over recent decades now focus on controlling inflammation and healing the gastrointestinal lining to prevent complications.

Feeling fine doesn't mean treatment can stop

Patients sometimes assume that being symptom-free means they no longer need treatment, but Walfish says this is a mistake. Inflammation can persist silently during remission, causing further damage. He stresses that sticking with medications, monitoring, and regular checkups is essential even without symptoms.

Diet and stress don't cause IBD, but they affect flare-ups

No specific food causes or cures IBD, though balanced meals and hydration support symptom management, especially after a flare-up. Stress doesn't cause the disease either, but it can worsen flare-ups. Walfish recommends good sleep, stress control, staying active, and maintaining a strong relationship with a treating physician as part of overall management.