German "Salhumin" Rheuma-Bath

My German friend has given me a packet of "Salhumin" rheuma-bath powder. She tells me the product is widely used in Germany in therapies for replacement surgeries and rheumatic diseases. She tells me make the water as hot as I can tolerate and soak for 20 min., then plan to lay down about 45 minutes. I am somewhat concerned, as my health is a little fragile at this point, additionally I have recently discontinued some serious medications and having some withdrawal symptoms. Could any of you can tell me more about this product and its safety. Thanks. Tweet