The main reason for this is the long-term use of laxatives containing anthraquin, such as rhubarb, aloe vera, senna, etc. All kinds of synthetic laxatives contain more or less of these ingredients, if you have constipation, it is best to consult a professional doctor, do not blindly use laxatives and a variety of intestinal cleansing tea and other products. If you have already had a friend of the large intestine melanosis, do not worry too much, because there is no evidence that the large intestine melanosis will be malignant, as long as you adjust the diet structure, stop using laxatives, the blackening of the large intestine mucosa, thickening and other pathological changes can have a certain degree of improvement, and even the blackening can disappear. Nigrosis can lead to more difficult bowel movements.