you have to be careful of where you use the brackets, and where not to use them.
using concatenation, groups them into groups of two. you can only concatenate 2 parts at a time
being the first group, bracket them. This makes them one part. after this,
now this means that there are still 2 "parts" there, because the brackets cause hair and the comma to form into 1 part.
(hair&", ")&(eyes&", ")
now, hair and first comma are part 1, with eyes and second comma being part 2
((hair&", ")&(eyes&", "))&skin
this should make everything in the brackets part 1, while skin is now part 2.
Haven’t tested it, but this should work now.