Diarrhea is where you frequently pass watery or loose poo. Some people may also have other symptoms, depending on the cause. It affects most people from time to time and is usually nothing to worry about. However, it can be distressing and unpleasant until it passes, which normally takes a few days to a week. The excessive loss of water in your poo can also sometimes lead to symptoms of dehydration, which can be serious if it’s not recognised and treated quickly.