For most people, cold weather is an inconvenience, requiring an extra layer of clothing or the thermostat to be turned up. For others, exposure to cold can trigger an allergic reaction severe enough to cause them to collapse.
Cold urticaria is a rare but potentially dangerous condition in which contact with cold temperatures causes the immune system to misfire. The results can be hives, swelling, pain and in some cases, life-threatening anaphylaxis.
