Well ok. That's an aluminum alloy with some interstitial elements that are toxic on their own but encased in the rest of the alloy matrix, AND it's anodized and dyed. So when you're touching it, you're not really touching the aluminum alloy, you're just touching the oxide layer. The oxide layer is very hard, even brittle, as it resembles a porous foam that hardened as it formed, and since it formed being dipped in a vat of dye, the dye colors the inside of the little foamy bubbles, and now as light shines through those hard bubbles, it reflects the color of that dye. Sure, your skin can absorb aluminum oxide if it's loose and small enough in particles for your skins pores to take in. And dye could be absorbed if it were free to "leak" out of those bubbles. But Apple's not using Bright Dip anodizing, so in this case its not really sitting in those bubbles wet, it just coated the inside of the bubbles as they were forming. In either case, if by some strange twist in the universe your oxide layer just decided to self destruct into a powder small enough for your skin to absorb it or the dye, but also cling to itself and not fall off until you touched it, you'd immediately feel a loose powdery substance on your laptop, see it streaky wherever you touched it, and see your fingerprints where it took the dyed cells from the surface. And you'd see blue dyed oxide powder on your fingertips.
That said, hospitals see people all the time that develop allergic reactions to some random thing when the body's immune system just doesn't recognize it and decides to play it safe & treat it like a poison. Sometimes just materials, sometimes medicines, sometimes parts of our own bodies. Out of 8 billion human bodies, you can't expect every last one to get every reaction right. If watching 4000 episodes of House have taught me anything, go see a doctor that acts like Sherlock Holmes and humiliate him into giving you a diagnosis.
