Cold urticaria is one of the more common forms of physical urticaria. As the name already suggests, cold is the trigger for the skin manifestations. “Cold” is to be understood in a very broad sense. Anything that is cooler than the human skin may be considered cold.
Each patient has an own individual threshold temperature. This is the highest temperature which still triggers a wheal. This means temperatures which are elevated above the threshold temperature do not trigger wheals, however all temperatures under the threshold temperature do so. The higher the threshold temperature, the more frequently will the patient have symptoms. In the course of the disease the threshold temperature remains relatively constant; however, it can be lowered by treatment.
The terms “cold urticaria” and “cold allergy” are often used synonymously. It is, however, not quite correct. Cold urticaria does indeed cause allergy-like symptoms, but it is not an allergy in the true sense of the word. An allergy is based on the formation of antibodies against a triggering substance, the allergen. An allergen is actually a harmless substance found in our environment, occasionally also a substance found in the body. An allergic reaction occurs upon contact with the allergen. As cold is not a material no antibodies can be formed against cold, therefore a cold allergy cannot exist. The precise mechanisms on which cold urticaria is based have not been fully understood yet. Presumably the processes taking place in the body as reaction to cold lead indirectly to the activation of mast cells in the skin and to the release of histamine and other inflammatory substances.
Cold urticaria is a common form of physical urticaria. In cold countries (e.g. Scandinavia) it is more common, in warm countries a little less common. Women are affected roughly twice as often as men, both typically in young adulthood in both sexes. The disease lasts on average for 5 to 8 years. In our latitudes the disease is clearly prevalent in winter.
In the case of cold urticaria wheals and/or swelling result from the direct contact of the skin or mucous membranes with cold of no matter what type (air, water, objects, beverages or meals, evaporated sweat). The wheals and swelling sometimes already appear during cold impact, usually however, a few minutes later. They disappear within a few hours. As a rule the skin reactions (wheals, flares, itching, burning, swellings) are limited to the spot of cold impact. Therefor in winter usually the unclothed parts of the body, such as hands and face, are affected. Many patients report that apart from the absolute temperature a quick change in temperature, i.e. a big difference in temperature (transition from warm to cold) may lead to the appearance of wheals.
Cold urticaria holds particular risks, which fortunately only rarely lead to severe complications. However, in the case of extensive contact with cold, for instance swimming in cold water, it can become dangerous. The literal “plunge into the cold water” can trigger a generalised urticarial reaction involving the whole body which can lead to a shock. Due to the histamine release the blood vessels are expanded and blood pressure drops. Even more fluid is taken from the circulation by the wheal formation which leads to a further drop in the blood pressure. As a result the blood supply to critical organs (like the brain, heart, kidneys) is reduced, which may end in unconsciousness and drowning.
Cold drinks or ice-cream can lead to swelling in the throat area of patients with cold urticaria. Such swelling may not only result in difficulty in swallowing, but also in respiratory distress, or to a complete respiratory obstruction.
Caution is required for cold urticaria patients during hospitalization and particularly during operations because infusion solutions that are not warmed to body temperature prior to intravenous application can trigger serious attacks of cold urticaria. The anaesthesiologist should therefore always be informed about the cold urticaria condition.
Cold urticaria usually appears for no known reason, however rarely develops as consequence of another disease. In this connection reports are found in literature on haematology diseases, infection from bacteria, viruses and parasites and preceding insect bites in some cases. It is, however, disputable as to which extent they play a causal role in the development of cold urticaria.
Diagnosis of cold urticaria is relatively simple. A test is first made to find out whether cold urticaria is really present. Various tests can be carried out, of which the so-called ice cube test is the most common and simplest test method. Hereby a melting ice cube in a plastic bag is placed on the skin of the forearm for 5 minutes and the formation of the wheals are analysed 10 minutes after the end of the test. A cold urticaria can be diagnosed much more precisely with an electronic testing device, the TempTest® (Ill. 13). Thereby a metal cooling element with a precisely defined temperature curve is applied to the skin. This not only allows for the determination whether cold urticaria is concerned, but also the precise threshold temperature.
Why is it of help for cold urticaria patients to know their personal threshold temperatures? It is the threshold temperature which is the skin temperature as from which level symptoms occur. The patient who knows his own threshold temperature can pay attention to protect his skin from this and colder temperatures and to avoid exposing it to such temperatures. Furthermore, the severity of the manifestation can be assessed. The higher the threshold temperature, the higher the activity of the illness is. Furthermore, the success of the therapy can be determined quite well and the best treatment found based on the threshold temperature. In rare cases of cold urticaria the skin does not react to local exposure to cold. In such cases a longer period of provocation or the use of another provocation test (cold bracelet, cold chamber) is sensible.
It is of utmost importance that patients with cold urticaria know all about their disease and avoid contact with cold. This includes, among others, wearing thick warm clothing, gloves, caps and scarves in cold temperatures, avoiding taking baths in cold water and avoiding ice-cold food or beverages. Nevertheless, complete avoidance, particularly when threshold temperature is high, is not possible in everyday life. As the causes of the disease are unknown for cold urticaria and as a rule remain unknown, the focus is clearly on the avoidance of symptoms.
Frequently cold urticaria patients are advised to undergo an antibiotics treatment, e.g. with Doxycycline. It may be sensible as the cold urticaria can be cured with it. However, no good studies on this treatment are available so far and it must be assumed that less than half the patients are relieved of their symptoms.
A non-sedative antihistamine should be taken daily (or prior to contact with cold) as protection against the occurrence of wheals, itching and swelling after contact with cold. Some patients have to take higher doses, i.e. two or even four tablets daily, to provide them with sufficient protection. Antihistamines are a protection against the effect of histamine, which is released when the skin of cold urticaria patients comes into contact with cold and which then triggers wheals and itching. (s. Section 1.3 “The mast cell as key cell”). Omalizumab is similarly effective in patients with cold urticaria as in patients with spontaneous chronic urticaria.
However, no explicit approval has been issued for Omalizumab for therapy of cold urticaria.
A further form of cold urticaria patients is the so-called cold desensitization treatment. The sensitivity of the skin to cold is lowered by taking daily cold showers. However, this treatment is complex, not entirely without risk and has to be initiated under inpatient conditions. This means it should not be tackled on one’s own initiative, but must, under all circumstances, be carried out by allergists or dermatologists.
High risk patients should always have an emergency kit on them. An emergency kit usually consists of a cortisone preparation and an antihistamine. Carrying an adrenalin auto-injector along makes sense for severe cases.