My bottom left eyelid started swelling and I don't know why or what to do?

So my bottom left eyelid was a little itchy today, and I scratched it once but then left it alone, then like an hour later, it started swelling and I have no idea why? Could it be an allergic reaction? Or a growth? If it helps, I'm at a ski resort in the Swiss Alps and the coldness affects the rate of absorption of moisture in my body, in other words, I get dry very quickly here. What should I do?