Epsom Salt is a natural laxative and you can relieve constipation by sitting in an Epsom Salt Bath.
To allow the Epsom Salt to work on your body and relieve constipation you should sit in the Epsom Salt bath for a minimum of 15 minutes.
But it may take 20 to 30 minutes of sitting in the Epsom Salt bath for the Epsom salt to work and relieve constipation depending on how severe the constipation is.