http://www.racingsmarter.com/epsom_salts.htm
Also, if you are using Epsom Salts, here is a tip: if you are near a farm store they sell it in 50 LB bags for about $20 but it's just called magnesium sulfate
Also, if you can't use baths (because your little Darling may drink the water) try using it as a lotion or cream which you can make yourself much cheaper than buying it prepared. (this was emailed to me from a mailing list, so I need to say "thanx Karen!")
For the cream:
Dissolve the salts with a little water, usually heating the water and salts in the microwave helps it dissolve better and then just mix into any cream you like. I bought 4 oz of cocoa butter at GNC in the mall. Mixed a little water with 3 tablespoons of epsom salts and dissolved it by heating in the microwave (about 1 minute). Then just mixed the salt water in with the cream. You can add more of less salts, but more than this and it leaves the white film and gets a little too itchy for me. Adding a little oil or coconut oil may help this if you like. I have also mixed the salts in leftover suntan lotion, primrose oil cream (2 oz for $1 at GNC), and some aloe vera cream (4 oz for $2 at the grocery). Pretty much any lotion your child can tolerate. You can buy large bottles of hand lotion or skin cream for just a few dollars in the grocer or other places. The salts will last a long time this way. I just couldn't justify paying $20 or more for 4 oz of something I could make just as well at home for far less.
For the oil:
Just mixing the salts with water would leave a salty film on the skin which my two boys and I didn't like (itchy). Lately, I have been mixing some coconut oil in with the salts and water. Actually it is more oil than water. 3 tablespoons water + 4 tablespoons salts + 12 tablespoon coconut oil. The coconut oil is good for the skin anyway and it seems to counter the drying effect of the salts. I found that just mixing the salts and oil did not dissolve the salts, so I needed to add just some water. I apply this liberally on the skin and it soaks in plus leaves the skin smooth and soft.