People who have watery, black diarrhea may be suffering from an infection, pancreatitis, irritable bowel disease or colon cancer, according to WebMD. Black stools are often accompanied by abdominal or rectal pain, fever, and signs of dehydration.
Chronic diarrhea can result from exposure to parasites or bacteria when people ingest contaminated food or water, explains Mayo Clinic. Certain medications such as antibiotics or viral infections also cause chronic diarrhea that can appear black and watery. People who are lactose intolerant yet consume dairy products often struggle with diarrhea.
Diarrhea is commonly accompanied by bloating in the stomach, cramps, an urgent feeling to have a bowel movement, and nausea or vomiting, according to WebMD.