Up to 20% of American adults have gastrointestinal symptoms labeled as “irritable bowel syndrome” (IBS). Syndromes are a description of symptoms, not the diagnosis of a root cause. The intestine does not have the capacity to be “irritable”—the intestine reacts to pathogens and parasites, the infectious cascade, dysbiosis, and changes in the microbiome. IBS is a syndrome in need of a diagnosis.