If you eat too many laxative products such as evergreen tea, there will be dense black stripes on the intestinal mucosa, which are leopard-like, called melanosis coli.
It is black because these laxatives contain anthraquinone. Anthraquinones can directly stimulate intestinal peristalsis, help defecation and induce apoptosis of intestinal mucosal epithelial cells. After the dead cells are swallowed by macrophages, lipofuscin is slowly produced in macrophages, and when lipofuscin is gradually concentrated, the intestinal mucosa will show this dark brown color.
Only laxatives containing anthraquinones can cause melanosis coli, mainly some plant medicines, such as senna and rhubarb.
Fortunately, melanosis coli has no clear health risks.
Although it is uncomfortable to look at the dark, this kind of melanosis coli is not very dangerous, and it will not further become worse things like colorectal cancer. There is not enough evidence to support previous concerns about possible cancer. Even, because of the strong contrast of mucosa blackening, which is equivalent to artificial staining, it may help colonoscopy to find small polyps.