When you have an open wound you should avoid soaking it in Epsom Salt since if you soak the open wound in Epsom Salt it could cause further infection or irritation of the wound due to the magnesium sulfate compound.
Soaking your skin though in Epsom Salt can help with skin conditions such as psoriasis and even help with blisters, sore muscles and other skin conditions.
But soaking an open wound in Epsom Salt should be avoided even though it may help the wound heal but then again it could irritate your wound more.