Sublimaze should probably answer, but my thinking is, I've eaten tons of mangoes, handled all sorts of them, and at times ate a little bit of the skin by mistake, and nothing happened to me, so I think yours would be an allergic reaction, since I did not get any reaction to mango skin.
p.s. glad you started this thread.
Oh, and since this is random questions, who were you on the old board? Your posts seem familiar!