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........

© The Conversation