What Is Chronic Spontaneous Urticaria (CSU)?

Chronic spontaneous urticaria (CSU) is the medical term for hives that:

• Have no known cause
• Last a long time

Chronic = Lasts for 6 weeks or longer

Spontaneous = No obvious cause or trigger

Urticaria = Red and itchy raised welts or patches on the skin (hives)

What causes CSU?

When your immune system detects a threat, it releases histamine and other inflammatory chemicals.

Histamine can widen blood vessels, which can lead to skin swelling, itchiness and redness.

What triggers hives?

Common triggers of hives usually include:

• Allergies
• Bacterial infections, including UTIs and strep
• Viral infections, including colds and mono
• Certain medicines, including antibiotics and ibuprofen
• Extreme hot or cold temperatures

Unlike other types of hives, CSU usually has no identifiable trigger and the cause is unknown. But it is often linked to type 2 inflammation .

Type 2 inflammation = an overactive immune response that can contribute to inflammatory conditions.

Treatments for CSU

• Antihistamines used first
• Biologics (monoclonal antibodies that target the immune system) if symptoms still aren’t controlled

Help for CSU

If you have hives that last 6 weeks or longer or keep coming back, talk to your primary care provider, dermatologist or allergist.

This educational resource was created with support from Regeneron and Sanofi.