Alloy has nickel in it. Nickel causes contact dermatitis for a lot of people, me included. My MBP does the same and is coated in vinyl sheet to stop it literally making my hands bleed.

Apple is one if the only vendors that actually doesn't actually consider biology when designing a product. Even the shittiest Lenovo or no brand Chinese clone laptops are made of better materials.

So I use my Lenovo instead and the MBP sits there like a lemon waiting until I can be arsed to clean it out and eBay it.

LOTS of people have this problem. My dermatologist said that he sees 3-5 people a week that have contact allergies on hands and ears that use apple products. I tried to email apple about it - never heard a thing back.

Edit: 2 days of using an MBP without vinyl around it: http://i.imgur.com/HgDquuE.jpg