Dave Delano writes:

Youth can be a great insulator, but we still need to wear more than running shorts in sub-freezing weather. Read the 1977 article in the New England Journal of Medicine on penile frostbite and you will likely lose your fear of tights. You may even find yourself shopping for your first pair of wind briefs.

The actual article doesn’t appear to be online, but you can get the important details — and treatment information — from this recent ABC News story.