Cold urticaria (CU), one of the more common forms of physical urticaria, is typically acquired, i.e. it develops over the course of a person's life. As the name suggests, cold is the trigger for the skin manifestations. It is typical for this condition that urticarial symptoms that only appear at skin sites that have been in contact with cold, e.g. with cold air or cold water.
Cold allergy or cold urticaria?
The terms "cold urticaria" and "cold allergy" are often used synonymously. It is true that a CU causes precisely the same symptoms as an allergy, but it isn't a real allergy. Other diseases, such as cryoglobulinaemia (where the blood forms special antibodies when cold) are also perpetually wrongly called "cold allergies." The term "cold allergy" is not just misleading, it is incorrect: one simply cannot be allergic to cold. Allergies are based upon the formation of antibodies against a triggering substance, the allergen. An allergen is a substance from our environment - and sometimes even present in our own bodies - that is in and of itself harmless. When contact is made with the allergen, an allergic reaction is triggered. Since no antibodies can be formed against cold, there cannot be anything properly called a cold allergy.
Among physical urticarias, CU is not all that uncommon (roughly 15%). It is more common in cold countries (e.g. Scandinavia), less frequent in warmer ones. Women are affected roughly twice as often as men, typically in young adulthood for both sexes. The average lengths of the condition is roughly 5 years. In our latitudes, the disease is clearly prevalent in winter.