The "curl it " eyelash culer is great I love it , it works well, better than any other I"ve used, metal or plastic.
Obviously, there's this one by Sephora. I can't vouch for it, but it is obviously plastic. The one I swear by is by Japonesque. I have the small one that curls your lashes in sections at a time. It works great on me (and is all plastic). If you're comfortable with it (some people aren't), there's the option of a heated curler. I know the reviews on Sephora's version is mixed, so take that as you will. My Japonesque one has always worked for me, and I assume that the heated curlers are generally about the same in construction. (The only metal on the curler you come in contact with is the coil that curls your lashes. It's encased in plastic - the Japonesque version, anyway - and only comes in contact with your lashes, nothing else. I mention this as an option since I know some who use the metal curlers will heat them with their hair dryer, but if you're intensely allergic, I guess heated curlers aren't so much an option either.)