Cold urticaria, also known as 'cold hives' is an allergy triggered by exposure to the cold which causes red welts to appear on the skin. These are often itchy and can be accompanied by redness and swelling in the hands and feet. The hives themselves can vary in size from around 7mm to 27mm in diameter. Cold urticaria can be congenital or acquired, and is most likely to occur between the ages of 18-25 in the latter case.
There are various types of cold urticaria. These include:
Primary Cold Contact Urticaria: Caused upon contact with windy weather and other cold environments resulting in the wheal response (a particular type of hive). Can be acquired.
Secondary Cold Contact Urticaria: This is also characterized by wheals, and is due to serum abnormalities such as cryoglobulinemia. These are often associated as well with other symptoms such as Raynaud's phenomenon (a change in color for the fingers or other extremities) or purpura.
Reflex Cold Urticaria: This is due to more generalized cooling of the body (rather than being subjected to a cold environment necessarily).
Familial Cold Urticaria: Of course a familial genetic condition which results in rash, conjunctivitis and chills when exposed to cold – or even temperatures just below 22 degrees Celsius. The condition is mapped to CIAS1.
Hives are caused due to the dilation of capillaries which enable fluids to flow out into the surrounding tissue. The body absorbs this fluid resulting in the lumps and redness. Pressing on the hive often causes the skin to blanch. These hives can last a few minutes or a few days depending on the person, and often result in a burning or itching sensation. In rare cases the condition can lead to hypotension which is potentially life threatening. If the hives appear after less than three minutes contact with the cold, this suggests the condition is more likely to be potentially dangerous.
The cause of the hives is a histamine reaction that occurs in response to cold stimuli – this might include a drastic drop in temperature. Cold hives can also be a result of other conditions and it is often advisable to test for these conditions. A diagnosis can be obtained by an allergist during which a cold piece of ice is often held against the skin to test for a reaction.
The recommended treatment is simply to avoid exposure or contact with extreme cold. This means wrapping up warmly and using wind protective clothing, it also means avoiding swimming in cold water, and perhaps even moving to a warmer climate. Swimming in particular can be dangerous as it causes an elevated heart rate and thus increases the chances of hypotension. Antihistamines may be effective but not always – though cyproheptadine is often found to be useful, as is ketotifen which prevents mast cells from discharging histamine. Someone who suffers from cold urticaria might be advised to consume one of these medications prior to going out on a cold day or swimming in cool water.