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.
The condition was first described in 1792 by a German physician called Johann Peter Frank. Today, we know it is almost twice as common in women than in men, with the average age of onset in the early twenties, though it can affect people at any age.
There is some good news: between 24% and 50% of people with the condition see improvement – or even full recovery – over the years.
There are two forms of the condition. Primary cold urticaria is the most common, accounting for about 95% of cases and often has no known cause. The remaining 5% are classified as secondary urticaria, which is linked to underlying conditions or infections, such as the Epstein-Barr virus, certain types of lymphoma (blood cancer), HIV and hepatitis C.
Primary cold urticaria typically causes a rash, swelling, bumps or hives, though some people also report fatigue, fever and aching joints. Symptoms usually appear when the skin is exposed to cold, but can also occur as the skin warms up again. Triggers aren’t limited to cold weather – they can include swimming, eating frozen food, drinking cold liquids and handling cold objects.
Aside from a few very rare genetic causes, why some people develop primary cold urticaria remains unknown. What is clear is that mast cells are involved. These sentinel cells act as first responders in the body’s tissues – including the skin – alerting the immune system to danger signals or germs.
What triggers their activation in cold urticaria remains a mystery, though one theory suggests that cold exposure causes the body to produce so-called autoallergens – substances that trigger an immune response against the body’s own tissues. Much more research is needed to understand how this happens.
When mast cells are activated, they release a chemical called histamine. Think of histamine as an alarm that alerts other immune cells to rush to the area. It also makes the blood vessels in that part of your body widen and become “leakier”, which causes the telltale swelling, redness and itchiness.
Normally, this response is helpful – the extra blood flow and leaky blood vessels allow immune cells to squeeze out of the bloodstream and into the surrounding tissue to fight off a genuine threat. But in cold urticaria, it’s a false alarm. Your body is mounting a full-scale immune response when there’s nothing to fight, causing discomfort without any benefit.
Doctors test for cold urticaria by placing an ice cube on a patient’s forearm and watching what happens after they remove it. This test typically follows patients noticing they develop welts, hives or rashes on exposure to cold things. This must be done by a medical professional because in about 20% of cases, it can trigger anaphylaxis.
The condition is quite rare, affecting six in every 10,000 people. But it may be underdiagnosed as not all sufferers have severe symptoms and, in some countries, particularly tropical ones, temperatures tend not to drop below 0°C in winter.
Once diagnosed, it’s important to help people with cold urticaria avoid or recognise their trigger temperatures. There are two measures that may be assessed, depending on the availability of measuring devices. One is the cold stimulation time test, which indicates how quickly your skin reacts to cold with a lump or rash (a shorter time suggests a more active response). The other measure is the critical temperature threshold, which is the warmest temperature that can still trigger symptoms.
Antihistamines and beyond
There are treatments that can help manage the symptoms. One approach is taking antihistamines before exposure to cold environments or stimuli.
For many people, though, a standard oral antihistamine dose isn’t enough. Sometimes, up to four times the standard dose may be needed. The trade-off is that some antihistamines can have a sedating effect, so caution is needed.
About 60% of people with cold urticaria respond well to treatment with antihistamines.
During short flare-ups, other drugs, such as corticosteroids, may be beneficial, although longer-term use brings side-effects, such as weight gain, indigestion and mood changes.
Severe cases can be treated with a monoclonal antibody called Omalizumab, which targets immunoglobulin E, a molecule involved in mast cell activation.
Another option is desensitisation: gradually exposing the skin to cooler temperatures over several days (although, sometimes over a few hours) to try to overcome the response and histamine release. There have been some successes with this approach, but most of the studies have been small.
For people with the most severe cases, adrenaline is a lifesaving option in response to anaphylaxis, though it appears to be under-prescribed in patients with cold urticaria.
People with this condition also face increased risk during surgical procedures, where anaesthetic drugs reduce core body temperature and operating theatres are kept deliberately cool. While warming measures are used during surgery, for people with heightened sensitivity to cold, this can present an additional risk.
As winter continues, it’s worth remembering that for some people, the cold isn’t just uncomfortable – it can be genuinely dangerous. Understanding and recognising cold urticaria could make all the difference.
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