Mesalazine should be mesalazine, taking mesalazine usually does not cause black stool, the appearance of black stool need to consider the possibility of diet or disease caused. The oral dosage form of mesalazine includes enteric-coated tablets, extended-release tablets and granules, etc. The instruction manual points out that the adverse reactions include headache, dizziness, nausea, vomiting, abdominal pain, diarrhea, gastrointestinal flatulence, changes in blood cell counts, peripheral neuropathy, renal dysfunction, myalgia, arthralgia, and transaminase elevation. No manifestations of black stools were noted. Mesalazine is used in the treatment of ulcerative colitis and acute exacerbations of Crohn’s disease. It is contraindicated in people who are allergic to the product, renal dysfunction, severe hepatic dysfunction, gastric or duodenal ulcers, and people with a bleeding-prone constitution. The appearance of black stools may be due to eating foods rich in melanin such as duck’s blood, pig’s blood, mulberry and so on. Or disease factors such as peptic ulcer bleeding and so on. If you have black stools, you can go to the hospital for a routine stool examination to find out whether there is bleeding, and if necessary, improve the colonoscopy. The reason for the black stool is clear, and follow the doctor’s instructions for targeted treatment.