Thank you for your great post on MSM, Art!
I think people do need to be very careful when they take MSM orally. I have taken it in the past and it caused anxiety and this sensation of pressure on the heart that was intense! I think that is a common side effect for people starting out on MSM.
Turns out you also have to be equally careful with dogs too! I gave a very small amount to my dogs in their dinner recently to help with arthritis and the next day, one of them wouldn't stop whining all day. He was clearly feeling punk from the supplement. No more of that! After 24 hours it left his system and he was back to his happy old boy self.
I will have to try it topically (on myself, not the dogs) and see if has the same side effects.