I just read an interesting article on clay as a possible use for fighting drug-resistant infections like MRSA:
The article makes mention of a French clay, so I did some digging and came across this:
"Montmorillonite is also used in animal feeds as an anti-caking agent. Current research indicates that montmorillonite or bentonite has the ability to bind mycotoxins in the digestive system of animals as well as several bacteria in-vitro."
I had no idea what mycotoxins were, but thankfully Wikipedia has the answer.
"Mycotoxin (from the Greek μύκης (mykes, mukos) "fungus") is a toxin produced by an organism of the fungus kingdom, which includes mushrooms, molds and yeasts."
I personally think that rosacea is caused by some kind of fungal overgrowth, so maybe this helps to explain it further.
By the way, I was taking bentonite about a month back and felt that it helped quite a bit with my digestion, which I think is the primary cause of my rosacea.