These are known as physical urticarias,and cold urticaria is one such.Antihistaminics help.You may need a blood test to rule out cryoglobulins as a rarity.
It can be due to cold urticaria. Cold urticaria is a chronic, reactive skin disorder. The population most affected is young adults age 18 to 25 years Severe reactions can be seen with exposure to cold water or cold things.This can cause a massive release of histamine resulting in low blood pressure, fainting, shock, and even death.
This allergic response can take several forms, from rashes to wheezing, hives, swelling and redness.
Cold urticaria is diagnosed by holding an ice cube against the skin of the forearm for 1 to 5 minutes. A distinct hive should develop if a patient has cold urticaria.
Patients with cold urticaria should learn to protect themselves from a rapid drop in body temperature.Antihistaminics like Claritin and zyrtec can also be taken. The antihistamine cyproheptadine (Periactin) has been found to be a useful treatment also.
Sometimes cold urticaria is a symptom of another problem, such as cryofibrinogenemia, cryoglobulinemia, or syphilis.So please contact a dermatologist/immunologist to get a more confirmatory diagnosis
Hope it helps.Take care and regards.