DMSO = dimethysulfoxide --it is a very potent solvent.
MSM -- methylsulfonylmethane -- a common supplement for arthritis/joint issues in supplements orally.

This has been around for a LONG time--decades.

The problem with it, is that it is basically a carrier...a solvent.
So it is can be used to carry other things into the body.
In fact it is used to treat some bladder disorders as an irrigating solution, introduced directly into the bladder. This is not common, but if you Google it you will find it.

So the skin should be very clean before using it.

I am unaware of its benefit for PN. But I will search it tomorrow to see if any newer data exists.

My continuing impression is that it is a double edged sword.
Good for arthritis etc, but perhaps not a cure all.