My Dad (86) has been suffering with extreme diarrhea off and on for the last four weeks. Any advice?

Time to visit the doctor. The diarrhea could be caused by many things -- medications, food sensitivities, intestinal problems, microbial infections. A physician should be able to tell what might be causing the problem. I hope he can find an effective treatment.

When diarrhea is frequent, has no apparent cause, and becomes a chronic problem, it may signal something more serious, such as colon cancer or inflammatory bowel disease. Call the MD and get a referral to a gastroenterologist.