Most people expect some discomfort when they step into frigid air or touch an icy surface. For those with cold urticaria, however, exposure to low temperatures can trigger an allergylike reaction that ranges from itchy hives to a potentially life threatening emergency.

Cold urticaria, sometimes abbreviated as CU, is a condition in which cooling of the skin activates immune cells and causes symptoms such as welts, swelling and itching. Although it is often described as a cold allergy, it does not necessarily involve an allergy to a specific substance. Instead, the body reacts abnormally to a physical trigger: cold temperatures.

The condition can appear suddenly, including in people who previously tolerated cold weather without a problem. In some cases, it eventually resolves on its own. Until then, identifying triggers and taking preventive measures can help reduce the risk of a reaction.

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What are the symptoms of cold urticaria?

Symptoms commonly begin within minutes of exposure to cold air, water, food, drinks or objects. They may become more noticeable as the exposed skin starts to warm.

Possible symptoms include:

• Red, itchy or raised welts known as hives
• Swelling of the hands after handling something cold
• Swelling of the lips after consuming cold food or drinks
• A burning sensation on exposed skin
• Swelling around the affected area
• Lightheadedness or fainting
• Difficulty breathing or wheezing
• A rapid heartbeat or drop in blood pressure
• Swelling of the tongue or throat

The severity of cold urticaria varies widely. Some people develop only a few hives on exposed skin, while others can experience a reaction throughout the body.

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Cold-water immersion is especially dangerous because a large area of skin is cooled at once. Jumping into a cold pool, lake or ocean can trigger a sudden, widespread response, including loss of consciousness, shock or drowning.

Can cold urticaria cause anaphylaxis?

In severe cases, cold urticaria can lead to anaphylaxis, an acute systemic reaction that requires immediate treatment. Warning signs include difficulty breathing, throat or tongue swelling, faintness, confusion and a weak or rapid pulse.

Call emergency services immediately if a person has trouble breathing, collapses or shows other signs of anaphylaxis after cold exposure. If an epinephrine auto-injector has been prescribed, use it as directed while waiting for emergency care.

Anyone who has experienced a serious reaction should speak with a health care professional about carrying epinephrine and creating an emergency action plan.

What can trigger a reaction?

Cold urticaria does not occur only during winter. Symptoms may be triggered by:

• Cold or windy weather
• Air conditioning
• Swimming or wading in cold water
• Rain, snow or ice
• Holding refrigerated or frozen objects
• Drinking an iced beverage
• Eating ice cream or other frozen foods
• Walking barefoot on a cold floor
• Rapid changes in temperature
• Medical procedures involving cold rooms, fluids or equipment

The temperature needed to cause a reaction differs from person to person. Cool conditions that feel harmless to one individual may be enough to cause hives in someone with cold urticaria.

Why does it happen?

During a reaction, cold exposure prompts mast cells in the skin to release histamine and other inflammatory chemicals. These chemicals cause blood vessels to widen and fluid to collect in the skin, producing redness, itching, swelling and hives.

In many cases, the underlying reason for this response is unknown. This is called primary acquired cold urticaria. It often begins in young adulthood, although it can affect people of any age.

Less commonly, cold urticaria may be associated with another health problem, such as an infection, an autoimmune condition or certain blood disorders. Rare inherited forms also exist and may cause symptoms that differ from the more common acquired form.

Because several conditions can cause unusual responses to cold, a medical evaluation is important — especially if symptoms are severe, persistent or accompanied by fever, joint pain, fatigue or other systemic problems.

How is cold urticaria diagnosed?

A clinician will usually begin by asking when symptoms occur, how quickly they develop and whether the person has ever experienced breathing problems, fainting or a whole-body reaction.

A cold stimulation test may be used. Traditionally, this involves placing an ice cube in a protective bag against the skin for several minutes and then watching the area as it warms. A raised welt may indicate cold urticaria. Some specialists use a temperature-controlled device to determine the temperature at which the skin reacts.

Cold testing should not be attempted at home without medical guidance. It could provoke a serious reaction, and some forms of the condition do not respond predictably to a simple ice test.

A health care professional may also order blood tests or other evaluations if there is reason to suspect an underlying condition.

How is it treated?

The first step is limiting exposure to known triggers. That does not always mean avoiding the outdoors, but it may require additional planning during cold weather or before activities involving water.

Nonsedating H1 antihistamines are commonly used to prevent or reduce hives and itching. Depending on the severity of the condition, a clinician may recommend taking one regularly or before an anticipated exposure. People should not increase a medication dose without medical supervision.

If symptoms continue despite antihistamines, an allergy or dermatology specialist may consider other treatments. Omalizumab, an injectable medication also used for certain cases of asthma and chronic hives, may be prescribed for cold urticaria that does not respond adequately to standard treatment. Treatment should be tailored to the individual’s symptoms and medical history.

People at risk for anaphylaxis may be advised to carry one or more epinephrine auto-injectors at all times.

How can reactions be prevented?

Several precautions can make cold exposure safer:

• Check weather and water temperatures before outdoor activities.
• Wear warm layers, gloves, a hat and protective footwear.
• Cover exposed skin in cold or windy conditions.
• Avoid abruptly entering cold water.
• Never swim alone, even if previous reactions were mild.
• Test water cautiously only according to a clinician’s guidance.
• Avoid iced drinks or frozen foods if they cause mouth or throat swelling.
• Use insulated gloves when handling frozen products.
• Take prescribed preventive medication as directed.
• Tell doctors, dentists and surgical teams about the condition because cold procedure rooms, intravenous fluids or equipment may trigger symptoms.
• Make sure family members, friends and coworkers know how to recognize a severe reaction and use an epinephrine auto-injector.

A person’s reaction threshold and severity can change. A history of mild hives does not guarantee that every future reaction will also be mild.

Cold urticaria versus a normal response to cold

Cold weather can make anyone’s skin red, dry, numb or uncomfortable. Those reactions do not necessarily indicate cold urticaria.

The condition is more likely when cold exposure repeatedly causes raised, itchy welts or pronounced swelling. Frostbite is different as well: It is a tissue injury caused by freezing and may produce numbness, pale or waxy skin, blisters and severe pain during rewarming. Suspected frostbite requires prompt medical care.

Does cold urticaria go away?

The outlook varies. Some people experience cold urticaria for only a few months, while others have symptoms for years. The condition can resolve spontaneously, but there is no reliable way to predict exactly when that will happen.

Even if symptoms appear to have stopped, it is wise to consult a health care professional before deliberately testing cold exposure or resuming activities such as cold-water swimming.

When to see a health care professional

Make an appointment if cold exposure repeatedly causes hives, itching or swelling, even when the reaction seems mild. A clinician can confirm the diagnosis, rule out other causes and develop a prevention and treatment plan.

Seek emergency care for breathing difficulty, swelling of the tongue or throat, fainting, confusion or other signs of anaphylaxis. Cold urticaria is often manageable, but recognizing the possibility of a severe reaction—and preparing for it—can be lifesaving.