...Skin exposed to the elements. 
Watching the 2014 Winter Olympics, I couldn't help but recall the sting of icy winds and snow spray, which comes along with alpine sport, and also, its consequence, red, chapped and frequently, sunburned skin.  Not a good look, short or long-term, and painful too! ...and if you are coming down a mountain at 60+ miles per hour, well, owh!!  Even if you are doing nothing more exciting than clearing your walk (and who among us isn't lately), you are not immune, unless you you take proper precautions.  That means layering protection.  Start with a heavy moisturizer.  Creams are better than lotions.  The more extreme the conditions the "goopier" your cream should be.  (I have been known to use heavy-duty hand cream on my face and have been glad of it.)  Follow that with a SPF 50+ sunscreen containing physical blocking agents zinc oxide and/or titanium dioxide and reapply often  -- as often as hourly at high altitude.  Be sure you coat all exposed skin including behind your ears and nape of neck.   And don't forget an SPF lip balm.  There are many on the market.  Pick your favorite, follow our advice, and your skin will have nothing to fear from the elements.