Why do I get hives during the winter months?

Cold urticaria. Urticaria or "hives" as they are commonly called, can be triggered by exposure to cold. Persons with cold urticaria often cannot hold a cold can in their hand without itching developing when the hand is re-warmed.
Ice cube test. The classic skin test for cold urticaria that dr. Vaughn described so well is placing an ice cube on a spot on your forearm. Check every 5 minutes to see if a hive appears. If no hive after 15 minutes remove the ice cube, sometimes the hive appears a few minutes later - that's delayed cold urticaria.