About CIU

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

CIU patient Vicki Lawrence folding laundry

What is Chronic Idiopathic Urticaria?

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

It can look and feel different for everyone, but all cases of CIU 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.

The three common factors of CIU are:

  • Chronic– lasts for six weeks or more
  • Idiopathic– there is no explanation for what is causing 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 pale when they are pressed in the center

Causes and Symptoms of CIU (Chronic Hives)

CIU Causes

Unlike other types of hives, there is no known cause of CIU. 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 CIU, speak with an allergist, who is trained to identify and diagnose the cause of hives. Allergists diagnose CIU by ruling out other potential causes, such as an infection or allergic reaction.

CIU Symptoms

Common symptoms of CIU 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 does CIU look like?

For illustrative purposes only.


What CIU is Not

CIU 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 make their CIU seemingly worse, what distinguishes CIU from other forms of hives is that there is no known cause.


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 CIU, these things won’t make their hives go away.


CIU 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.


CIU, on the other hand, has no known cause. 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.


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

Think you have CIU? Talk to your doctor.

Learn What to Ask

Learn About a Treatment Option for CIU