*sigh*
Firstly, "bath salts" is a term that covers a VERY broad range of drugs. Almost any research chemical (phenethylamines, tryptamines, dissociatives, stimulants, empathogens, cathinones, piperzines, almost anything) can be sold as such, so calling a drug "bath salts" is obscure to the point of being almost meaningless. It's too ambiguous of a term.
Regarding the safety profile of DXM, the general consensus seems to be that moderate, occasional DXM use is fine (don't combine with any other drugs tho, except weed.) Long term heavy use will definitely mess up your brain...there are some case studies out there. If you choose to use DXM, make sure you get the product that has DXM as the ONLY active ingredient. If it has guaifenisen, you'll puke your brains out, and if it has acetaminophen in it you could die. DXM (like all drugs) is safe if you know what you're doing, but has the potential to be extremely dangerous if you don't. Hope that was helpful