In dreams, diarrhea often can be interpreted as being out of control or not being able to hold back emotions. Some people experiencing bad diarrhea might feel like they have been soiled due to embarrassing the stain or excreting in less than glamorous ways.
Dreams represent everything about ourselves and it is for this reason that a dream about going to the bathroom means that we have some strong feelings about whatever it may be. In fact, remembering that we went to the bathroom in a dream can symbolize us releasing these feelings, letting them ooze out in different ways than how we would let them in waking life.
To decipher what diarrhea means in a dream, first you have to determine the feelings somebody has been suppressing. In too many cases in real life, bowel movements or diarrhea will be required to take away the built up tension and overflow of emissions. While seeing this in a dream can make it seem like a bad thing, it is actually necessary.