India, May 28 -- Freaky flashback, but let's go with it. You're ready to embrace that snow-dusted Nordic town and walk around with that cup of hot cocoa before you hit the ski slopes in Lapland. Or perhaps it's the Tanzanian safari of a lifetime and you cannot wait to take in the unending expanse of the Serengeti grasslands. You've packed, you've planned, and you're ready. Well, almost. You didn't account for how your skin would feel about that dry winter cold, or even the dust that envelopes you as you pop your head out on the safari. The same reminds you of the oh-so-humid holiday in Indonesia where unexpected acne showed up on your otherwise clear skin. The terror!

But the answer to why is simple, sort of. Changes in climate, long-h...