Mechanism of PERK - eIF2a Pathways in Intestinal Mucosal Barrier of IBS-D and the Role "Metabolism Ingredients" of Tongxieyaofang

Inclusion Criteria: * Patients meeting the diagnostic criteria of Western medicine for IBS-D; * aged 18-70 years old; with a baseline IBS-SSS score over 75 points; * voluntarily signed the informed consent; * local resident who could ensure follow-ups, with basic reading ability Exclusion Criteria: * Patients with IBS-C, -M, and uncertain forms; * accompanied with serious lesions in major organs including heart, liver, and kidney, hematopoietic system diseases, and tumors; * gastrointestinal organic disease (e.g., chronic pancreatitis), or systemic diseases affecting the digestive tract motion (e.g., hyperthyroidism,diabetes, chronic renal insufficiency, and nervous system diseases); * undergoing or requiring constant use of drugs that may affect gastrointestinal functions (e.g., anti-cholinergic drugs, calcium channel blockers, 5-HT3 receptor antagonist, antidiarrheal agents, antacids, prokinetic agents, antidepressants, anxiolytics, and intestinal flora regulating drugs); * with history of abdominal surgery (e.g., cholecystectomy); * with an allergy history of tested drugs or severe allergy history of food; * pregnant and lactating female; * with a history of neurological or psychiatric disorders; * or participating in other clinical trial.