RSD when diagnosed needs to be treated first and foremost, with appropriate medicine and known and established treatments for it.

Bathing your limb in epsom salts is not an RSD treatment, but it can ease the pain a little. Whether that has anything to do with water temperature or the actual product... who knows? Fact is, you can't bathe your limb 24/7. Cherry pit pillows might help a little too. When bathing, just don't use hot water, cold water or ice... no extremes. Keep it lukewarm to warm, whatever you use.