I think it could be deadly for at least some people.

I tried MSM, the smallest dose that they recommend. I had heart palpitations from it. This happened twice so I know it was the MSM, which I then tossed out.

I have always had a fine heart & medical tests have never shown any problem. I really wonder what might happen to someone who had some heart weakness, maybe one they didn't even know about. I really wondered if some people have died later (my palpitatioins came up several hours after taking the MSM) and others had no clue as to the cause.

It is a very toxic mix of chemicals. Others have expressed serious misgivings about it also, on CZ. Mho.