Cave salt treatment (salt caves/grottos)

I have recently come acroos some info about healing properties of cave salt. What I found out is that in some countries like Russia, Poland or Slovakia facilities known as salt caves/grottos are built and that staying inside them for some time can contribute positively to your physical condition and even help in curing some diseases (asthma, bronchitis, etc). I was therefore curious if anyone on the forum has heard about such treatment and if it really works?! I have visited a Polish manufacturer website and must admit that their products are quite impressive but I have no idea if they really help. Any comments on this topic will be of paramount value to me.