I am using colloidal Silver topically for a muscle problem with some success. I am now considering mixing in a little bit of DMSO into the colloidal silver to increase penetration through the skin and into the muscle.

What I'm wondering is, what kind of an effect might the DMSO have on the silver?

It is hard to say.  But my question would be why?  The silver particles in the colloidal silver are supposed to be so small that they are readily absorbed.  So why would anyone want to add an industrial solvent that can possibly form new compounds to the silver?  For example  in this short abstract:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGB-4K605FH-P&...

Personally I am not a big fan of DMSO anyway.  It can also carry contaminates on the skin, such as soap scum, in to the bloodstream if the area is not cleaned properly.  And I have read on other boards of people wanting to combine it with oxidizers, which I really do not recommend.  This can lead to toxic byproducts.

DMSO is dimethyl sulfoxide. I am specifically worried about the oxygen content off the DMSO and whether or not it could oxidize the silver in the colloidal silver?

Off hand I would say that it is most likely to forma sulfide or sulfate.

Or do you think the sulfur/oxygen bond in the DMSO is so strong that it would not oxidize the silver?

According to the abstract above it looks like DMSO can react with silver, which means it would no longer be colloidal silver.