Chronic spontaneous urticaria is a puzzling skin condition that causes itchy hives to appear repeatedly for weeks, months, or even years—often without any clear reason why.

What Is Chronic Spontaneous Urticaria?

Chronic spontaneous urticaria, also called chronic idiopathic urticaria, is a condition where raised, red, itchy bumps called hives (or wheals) appear on the skin at least twice a week for six weeks or longer. These hives can show up anywhere on the body and usually fade within 24 hours without leaving scars or marks. However, new hives often replace the old ones, creating a cycle that can last for months or even years.^[1][3]

The word “spontaneous” describes how these hives appear without a specific, identifiable trigger. Unlike acute hives that might develop after eating a certain food or taking a medication, chronic spontaneous urticaria happens unpredictably. The term “idiopathic” means that in most cases, doctors cannot find a clear external cause. This uncertainty can be frustrating for people living with the condition, as they often cannot pinpoint what brings on their symptoms.^[2]

Between 30% and 50% of people with chronic spontaneous urticaria also experience angioedema, which is swelling in deeper layers of the skin. This swelling can affect the lips, cheeks, eyelids, hands, feet, or genitals and may cause a burning or tingling sensation rather than itching. Unlike hives, angioedema can take up to 72 hours to disappear.^[3][7]

How Common Is This Condition?

About 1 in 4 people will experience hives at some point in their lives. However, chronic spontaneous urticaria is less common, affecting approximately 0.5% to 1.4% of the general population at any given time. Some estimates suggest that up to 400,000 people in the United States may struggle with chronic hives.^[1][3]

This condition can occur at any age, but it most commonly begins between the ages of 20 and 40 years. Some studies note that the condition peaks in people during their 30s to 50s, affecting individuals during their most productive working years. Women are affected about twice as often as men, though the reasons for this difference are not fully understood.^[2][3][5]

Chronic spontaneous urticaria can also occur in children, although it is less common in this age group. When it does happen in children, it tends to affect older children and teenagers more than younger ones. The condition can have a substantial impact on quality of life, affecting school performance, work productivity, and sleep.^[3][11]

What Causes Chronic Spontaneous Urticaria?

For up to 95% of people with chronic spontaneous urticaria, the exact cause remains unknown. This is why the condition is called “idiopathic.” Unlike acute hives, which are often triggered by allergic reactions to foods, medications, or insect stings, chronic spontaneous urticaria is rarely caused by external allergens. In fact, patients with this condition often believe that food allergies are responsible, but research has shown that for almost all patients, foods are not the trigger.^[1][2]

Scientists believe that chronic spontaneous urticaria may have an autoimmune basis in many cases. Autoimmune conditions occur when the body’s immune system mistakenly attacks its own healthy tissues. Studies have found that about half of people with this condition have autoantibodies—specifically immunoglobulin E (IgE) autoantibodies—that may activate certain immune cells and trigger hives.^[3][7]

People with chronic spontaneous urticaria are more likely to have other autoimmune diseases. Conditions such as thyroid disease, celiac disease, lupus, rheumatoid arthritis, type 1 diabetes, and Sjögren syndrome appear more frequently in patients with chronic hives than in the general population. In particular, thyroid disease is commonly associated with chronic spontaneous urticaria.^[2][5]

Although the condition is not typically caused by infections, some cases have been linked to underlying health issues such as sinus infections, H. pylori bacterial infections in the stomach, liver disease, or even certain cancers like lymphomas. However, these associations are relatively rare.^[5]

Who Is at Higher Risk?

Certain groups of people are more likely to develop chronic spontaneous urticaria. Women, as mentioned earlier, are at higher risk than men. People who already have allergies, eczema, asthma, or food allergies may also be more prone to developing chronic hives, although the condition itself is not caused by typical allergic triggers.^[2]

Individuals with autoimmune disorders face a higher likelihood of experiencing chronic spontaneous urticaria. About 1 in 5 people with chronic hives also have an autoimmune disease. If you have been diagnosed with conditions like thyroid problems, lupus, or rheumatoid arthritis, your risk may be elevated.^[5]

People with a history of certain infections or chronic inflammatory conditions may also be at greater risk. However, it is important to note that chronic spontaneous urticaria can affect anyone, even those without any known risk factors or pre-existing health conditions.^[2]

What Are the Symptoms?

The hallmark symptom of chronic spontaneous urticaria is the repeated appearance of hives. These hives are raised, itchy welts that can vary greatly in size and shape. They may be as small as a pinprick or as large as a softball. The hives can be round, ring-shaped, or form large patches that look like a map. They are usually red or pink, but when you press on the center of a red hive, it often turns white—a phenomenon called blanching.^[1][5]

Each individual hive typically lasts between 30 minutes and 24 hours before fading. However, new hives often appear as old ones disappear, creating a frustrating cycle. The hives can show up anywhere on the body and tend to be distributed widely. Some people notice that certain areas are more affected than others.^[2][11]

Itching is a common and often intense symptom. The itchiness can be severe enough to interfere with daily activities, work, and sleep. Some people describe the sensation as burning or stinging rather than itching. The area around the hives may feel warm to the touch.^[2][5]

When angioedema occurs alongside hives, people may notice swelling in the lips, cheeks, eyelids, hands, feet, or genitals. This swelling can be accompanied by numbness, tingling, or a feeling of tightness. Unlike hives, angioedema can last up to 72 hours. In some individuals, angioedema may occur without any visible hives.^[2][7]

Can Chronic Spontaneous Urticaria Be Prevented?

Because the exact cause of chronic spontaneous urticaria is unknown in most cases, there are no specific measures to prevent the condition from developing in the first place. However, once you have been diagnosed, you can take steps to reduce the frequency and severity of flare-ups.^[2]

Identifying and avoiding personal triggers can be helpful. While chronic spontaneous urticaria does not have a clear external cause, certain factors can make symptoms worse. Common triggers include stress, alcohol, tight clothing, extreme temperatures (both heat and cold), hot showers, spicy foods, physical pressure on the skin, and certain medications like nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen.^[2][7]

Keeping a diary of your symptoms can help you identify patterns. Write down what you were doing, what you ate or drank, and any stressful events before your hives appeared. Over time, you may notice connections that can guide you in avoiding triggers.^[2]

Managing stress is particularly important. Stress is one of the most common triggers for chronic hives. Techniques such as yoga, walking, breathing exercises, meditation, or therapy can help you better manage stress and may reduce the frequency of flare-ups. Getting enough sleep is also essential, as poor sleep can weaken your immune system and increase stress.^[14]

Making adjustments to your clothing and daily routines may also help. Wearing loose, soft cotton clothing instead of tight or scratchy fabrics can reduce irritation. Avoiding very hot or very cold water when bathing, and limiting sun exposure by using sunscreen and protective clothing, may prevent hives in some individuals.^[14][16]

How Does Chronic Spontaneous Urticaria Affect the Body?

The physical changes that occur in chronic spontaneous urticaria involve the immune system and certain cells in the skin called mast cells. Mast cells are part of the immune system and are found throughout the body, including in the skin. They play a role in fighting infections, reducing inflammation, and helping wounds heal.^[6]

When mast cells are activated, they release chemicals, including histamine, into the surrounding tissue. Histamine causes blood vessels to leak fluid into the skin, which leads to swelling, redness, and itching—the hallmark signs of hives. In chronic spontaneous urticaria, mast cells are activated repeatedly, even though there is no clear external trigger. This ongoing activation is what causes the chronic nature of the condition.^[6][9]

In people with an autoimmune form of chronic spontaneous urticaria, the body produces autoantibodies that mistakenly signal mast cells to release histamine and other chemicals. These autoantibodies essentially trick the immune system into thinking there is a threat, even when there is none. This results in the continuous appearance of hives.^[3][7]

Mast cells also release other substances, such as cytokines and arachidonic acid metabolites, which contribute to inflammation and further swelling. This complex immune response explains why chronic spontaneous urticaria can be difficult to control and why it persists for such long periods.^[7]

It is important to understand that chronic spontaneous urticaria is not a dangerous or life-threatening condition in most cases. The hives themselves do not cause permanent damage to the skin. However, the condition can have a profound impact on daily life, sleep, work, relationships, and emotional well-being.^[3][6]