Epsom salts cause you to sweat, which is the central purpose of a detox bath. Drugs, toxins and poisons in your body will escape through the pores in your skin. Pour one cup of Epsom salts under the tap as you draw a very hot bath. You want the water to be somewhere between 95 and 100 degrees F. Soak in it for about 20 to 30 minutes, though you shouldn't soak any longer than that. As the water cools, the toxins will be sweated out of your skin. Check with your doctor first if you have diabetes or high blood pressure, since a detox bath might not be safe for you. Also, be sure to drink lots of water during and after the bath, to replenish the liquids you've sweated out.