I don't think I'm allergic to anything and from all the crap that I've inhaled over the years I don't think a little brass is going to kill me, but personally I don't like what it does to the taste, not so sure I can taste the chrome or nickel, sometimes I think I can, but brass gets me right away. some say it's no good for health reasons, don't know much about that, there are many thousands of cheap pv's out there that have chrome and/or brass exposed to
juice really, for me it's the taste that gets me and it affects my teeth, causes me to grind for some strange reason, nichrome wire does this to me also, same thing, metallic taste and teeth grinding, but then again I never claimed to be normal, so
the rm2 is a great little atty if the tastes of these metals don't bother you, and it seems most don't have any issues with it either, but if you know you have issues with brass or nickel or chrome then I'd say it's best to just stick with a stainless steel atty... off the top of my head, for a cheap atty for the non milled reo I would suggest the a6s, already set up with a bottom hole in the post so bottom feeds out of the box, full stainless steel, all you need to do is drill the air hole in the cap, or, if you're not opposed to drilling a center post then the igo s is a great little atty and also cheaper than the rm2, around the same size as an rm2 internally too, making it better than the a6s on that front, the a6s has a larger chamber and taste is not as great as a tiny chamber imo... I did my igo s and it had a stainless steel center pin so it was fine but I've seen others say that the new igo s actually has a brass center pin anyway, so that might not be best... once you go milled then your choices open up immensely, there are plenty of great stainless steel atty's out there
the center pin is the juices path so even that little bit can be enough to affect it, but then again even the reo's internal center pin that connects to the
juice bottle in the 510 connection is brass, so all stock reo's have at least some brass in the
juice path. I replaced mine with a stainless steel center pin so now no brass at all

for those affected by brass, is the amount of brass in the center pin alone enough for you to detect it? I can't say for sure because I only used the brass center pin for less than week, and always with the rm2 as well, so can't really judge how much difference the center pin alone might make... at least juice doesn't pool and stay in the center pin so I assume the problem is much more with something like an atty where juice sits than just the 510 pin itself...