About CSU

Learn more about CSU, a form of chronic hives, including causes and symptoms.1

CSU patient Vicki Lawrence folding laundry

What is Chronic Spontaneous Urticaria?

Chronic spontaneous urticaria, or CSU, is the medical term for chronic hives that have no known cause.

It can look and feel different for everyone, but all cases of CSU result in itchy hives that last for six weeks or longer. This can result in raised red bumps that may grow, spread, change, disappear and reappear on the skin. It is also sometimes referred to as chronic idiopathic urticaria, or CIU.

The three common factors of CSU are:

  • Chronic– lasts for six weeks or more
  • Spontaneous– there is no explanation for what is triggering the hives
  • Urticaria– this is the medical term for hives, pronounced “ur-ti-kair-ee-uh,” which are itchy, red, raised bumps on the skin that turn white when they are pressed in the center

Causes and Symptoms of CSU (Chronic Hives)

CSU Causes

Unlike other types of hives, there is no known trigger of CSU. This makes it harder to diagnose and treat than other conditions, and it may take some time before you are diagnosed. If you think you might have CSU, speak with an allergist, who is trained to identify and diagnose the condition. Allergists diagnose CSU by ruling out other potential causes, such as an infection or allergic reaction.

CSU Symptoms

Common symptoms of CSU include:

  • Red, raised circles on the skin, called “wheals”
  • Itching
  • Hives that may get bigger, change, disappear and reappear or spread
  • Hives that turn white, or “blanch,” when they are pressed in the center
  • Wheals, or hives, that occur most days of the week and last for at least six weeks

What could CSU look like?

For illustrative purposes only.

What CSU is Not

CSU is not caused by allergies or an infection, and it is usually not life threatening. It also is not contagious and it is not caused by a reaction to the sun, stress, hormones, foods or other medical conditions. While some people may identify things that seemingly make their CSU worse, what distinguishes CSU from other forms of hives is that there is no known trigger.

People who have chronic hives often think the hives are caused by something they’ve done or interacted with. Many people will go through an “elimination diet,” meaning they take foods out of their diet and slowly add them back to see if they have a reaction. They may also try to change products like soaps and detergents. For people with CSU, these things won’t make their hives go away.

CSU vs Hives

Hives are common, and many people will experience them in their lifetime. They are caused by swelling of the skin when the body releases a chemical called histamine and other chemicals into the blood. Often, people with allergies get hives. Hives can also be caused by insect or animal bites, a reaction to medications, allergies to pollen or dander, a food allergy, extreme stress, infections or illnesses. Most cases of hives last for only a few hours or days.

CSU, on the other hand, has no known trigger. Often it’s diagnosed when other causes of hives are ruled out. The hives last for six weeks or longer and can last for several years.

What’s the difference between a primary care doctor and a specialist?

Primary care doctors may care for adults (internal medicine), children (pediatrics) or both (family medicine). They have a broad range of medical knowledge and can diagnose and treat many common conditions. They also can refer patients to other doctors who are experts in certain conditions or diseases.

Specialists have additional years of training in a specific area of medicine, and they may offer specialized tests to diagnose illness. They also receive ongoing training in the latest medical research and treatments in their specialty. Allergists are specialists who care for patients with asthma and allergic conditions.

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  1. Vicki Lawrence is compensated for her involvement as a spokesperson for the CSU and You campaign.

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