Ok you have to realize that a lot of people use this forum for marketing. From getting doctors appointments to selling vitamins, foods, footpads, books and other trinkets.
I think if you buy into such things then the safest thing would be to pick up a high-school level or even first year university biology book and learn the basics of how your body works. Otherwise you are going to fall victim to every fad or scam under the sun.
You skin has one purpose. To keep the external environment separate from the internal environment. Under your skin you have many layers of tissue. Although your skin can absorb to limit extends water and salt and some other elements, it does a pretty good job keeping the internal environment isolated. The stuff that is absorbed by your skin does not penetrate very deeply at all. For example if you are dehydrated and you jump in a pool you can still die from dehydration. If you have a salt deficiency and your roll around in box of salt naked, you will not replenish your body. In the same way these bath cannot strip your internal body of much needed minerals. Your skin actually is an organ and is isolated from your internal functions.
If you swim all day, you can strip your skin of minerals like salt, but it isn't going to through your electrolyte balance out of whack for your system.
How is a mud bath going to get mercury from your
-and fat cells
out? It can't and that is were mercury is stored. You can only mobilize this mercury internally. If anyone tells you otherwise demand that they explain to you exactly how it works by explaining the complete biological pathway. They won't be able to because its a scam. All the other things can be totally explained.
Further, mud can and does have high amounts of aluminum, arsenic and other wonderful "minerals" as such. Make sure you get your minimum daily recommended dose of these things and don't forget to leave a tip. Course don't forget to get a second job and to pray a lot because you will need a lot of money and about 100 years to cheletae with something like that.
Although you can sweat out some mercury from what I have read, it is so little that it is beyond ridiculous to even talk about. Also that would probably be from free blood mercury. In other words mercury that has been mobilized from fat cells by something like chlorella or DMSA. In short, chelating with baths instead of mobilizers is just plain stupid. Now if you want to add baths...more power to you.
Though considering how improbable it is for the mud to have less toxins than your are going to get rid off, you are probably much better off without it. Remember even giants like Coca-Cola use tap water, lie and sell it as bottled water. Huge scandal in Europe. You think anyone is gona purify mud? Reality check. They scoop it were they find it. You can find people to buy anything these days.
There might be better buy in this forum someplace. There are some magic crystals that can re-grow your teeth and stuff. Very powerful so make sure you get advise before you proceed. Also growing some extra ones is good idea...you know, just in case ;) The consultation is the key..if you don't know how to use it they can't be held responsible for the results.