Chronic spontaneous urticaria (CSU) is a long-term skin condition characterized by itchy hives that last for at least six weeks. Unlike acute hives, which usually disappear within a few days, CSU can come and go for months or even years.
For hives to qualify as CSU, they must last for at least six weeks.
Around half of people with CSU see their symptoms clear up within the first six months. For others, symptoms linger for years, though it’s rare for the condition to last beyond 10 years.
The individual hives—itchy, raised bumps that often appear red or brown, depending on skin tone—usually last for no more than 24 hours. However, with CSU, new hives continually pop up as older lesions fade. People will usually experience hives almost daily. This continuous cycle means your skin rarely feels completely clear without medical treatment.
There are two main kinds of hives—chronic and acute hives. The primary difference between them is the duration of symptoms.
Acute hives (urticaria) are very common and are usually caused by a specific allergy to food, medication, or some other environmental trigger. These hives usually resolve within a few days and don’t exceed the six-week mark.
But with CSU, symptoms persist much longer because they’re not usually caused by external allergens. Evidence suggests that the majority of CSU cases are caused by internal, autoimmune issues. Essentially, the immune system mistakenly identifies healthy cells as a threat and triggers the activation of immune cells under the skin, which leads to the formation of hives.
The result is a constant state of alert, where your body keeps producing new hives. Because CSU isn’t caused by something you ate or touched, there’s no single outside allergen you can identify and avoid to stop the reaction.
Though CSU is a long-term condition, several key factors may determine how long your symptoms might stay active:
- Symptom intensity: If you have frequent, intense flares, your recovery may take longer than someone with milder symptoms.
- Angioedema: About 40% of people with CSU also experience angioedema, or swelling deep under the skin, usually near the lips, eyelids, genitals, or extremities. People with angioedema tend to have more persistent hives.
- Other health conditions: Having another autoimmune disorder, such as thyroid disease, can make your CSU timeline more complex. The same may be true for CSU patients who have high blood pressure, though more research is needed.
- Medication choice: There are a number of treatment options available for CSU. Some people respond to first-line treatments, while others may continue to experience symptoms until they find an effective treatment plan.
- Inflammatory markers: Your body’s internal inflammatory markers, like C-reactive protein (CRP), are linked to CSU severity. Having more CRP in your body could be a signal that your immune system will remain on high alert.
CSU is not usually a lifelong condition, and most people eventually enter remission. Remission means the hives stop appearing entirely for an extended period.
The likelihood of CSU remission increases over time. Half of people reach remission within six months, while about 80% of all cases clear up within three years. Around 8% of people with CSU experience symptoms for decades.
Remission for CSU is usually permanent, though it’s possible for the disease to come back later in life.
If you’re concerned that you may have CSU, there are some steps you can take to help you get diagnosed and treated:
- Keep a symptom log: Track how many days per week you experience hives, and pay attention to anything that might be triggering your symptoms. This can help your doctor confirm a CSU diagnosis.
- Consult a specialist: Ask your healthcare provider for a referral to a dermatologist, immunologist, or allergist if your hives have persisted for more than six weeks. Working closely with a specialist can ensure your symptoms are managed effectively.
- Review medications: Discuss long-term management options, such as non-drowsy antihistamines or the injectable drug omalizumab, rather than relying on temporary fixes.
- Monitor for severe symptoms: Seek immediate care if your hives are accompanied by swelling of your lips, tongue, or throat. These could be signs of anaphylaxis, a rare but serious condition.
