An Epsom Salt bath can cause diarrhea in some people if you take too many Epsom Salt baths or stay in the Epsom Salt bath for too long.
The Epsom Salt bath can help you relax your gut and relieve constipation and get your bowels moving and have a laxative effect.
The magnesium sulfate that Epsom Salt contains is what causes the laxative effect so yes diarrhea is one of the side effects of an Epsom Salt bath.
Consuming Epsom Salt can also relieve constipation because when you consume Epsom Salt it can give you an upset stomach, bloating as well as like I mentioned diarrhea.