Epsom salt is chemically called magnesium sulfate. Many years ago it was taken by mouth as a laxative, but it wasn't used much because it tasted so bad. There appears to be no scientific reason why epsom salt would be any better than table salt for common soaking. Soaking in warm water alone can be very soothing, due to the warmth of the water.
Did you know that soaking in epsom salt can actually make your foot problem worse?
Soaking your foot in epsom salt, or any salt (even the Pacific Ocean) does one thing very well-- it dries the skin on your feet by drawing out the moisture. So if you have dry skin, it will become even dryer after soaking in epsom salt. Soaking your feet in Betadine is drying as well and should be avoided if your skin is dry. Your calluses will hurt more, the cracks in your heels will deepen and your skin will itch more.
Please e-mail with any questions.