What Is Chronic Idiopathic Urticaria (CIU)?

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Chronic idiopathic urticaria (CIU) is the persistent, often daily appearance of hives (urticaria) that last for six or more weeks for no known reason. These hives are often itchy welts or bumps that appear when a trigger in the body causes mast cells to release histamine, serotonin, or other chemicals under the skin.

In general, hives are usually caused by a known trigger—often an allergic reaction or a viral infection that usually goes away on its own after a short time. The same cannot be said about CIU.

CIU occurs mysteriously and is not contagious. Compared with acute urticaria, it is harder to diagnose, and it presents with symptoms that can last for weeks, months, or even years.

This article will discuss the causes, symptoms, diagnosis, and treatment of chronic idiopathic urticaria.

Person scratching itchy hives

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CIU Causes

The precise cause of chronic idiopathic urticaria is unknown. Some research points to an altered gut microbiome (the community of different types of bacteria that live in the intestines) as a possible cause based on its important role in the function and regulation of the immune system.

Known causes of chronic urticaria, like viral infection with hepatitis or herpes zoster, and bacterial infection with Helicobacter pylori, must be ruled out before a diagnosis of CIU can be made.

CIU Symptoms

CIU is characterized by several symptoms, including:

  • Hives are the main symptom of CIU and may appear as wheals (skin-colored welts) or bumps with or without angioedema (swelling underneath the skin)
  • Pruritus (itchy skin) is produced by the release of histamine, serotonin, and other chemicals under the skin
  • Pain
  • Burning

If any of the following symptoms accompanies your itching, it may indicate an underlying medical condition or medical emergency, and you should seek immediate medical attention:

  • Fever
  • Chills
  • Shortness of breath
  • Swelling of the tongue, mouth, lips, or throat 
  • Generalized pain or body aches
  • Gastrointestinal symptoms such as nausea, vomiting, stomach cramps, or diarrhea


CIU is characterized by random and persistent hive outbreaks that last for weeks or months, with no known causes. A healthcare provider, often a primary care physician or a dermatologist, most commonly makes this diagnosis after issuing a battery of tests. The presence of hives for six or more weeks makes the diagnosis of CIU more likely.

CIU is often a diagnosis of exclusion that is made after a healthcare provider has evaluated the person for other possible causes to no avail. As a result, CIU can be a frustrating condition to diagnose, involving a long and extensive workup that may include trying a series of treatments along the way.

There are no specific labs or tests for diagnosis, but your medical history or physical exam may indicate the need to check specific inflammatory biomarkers (measurable substances that are a sign of infection) that may be associated with your symptoms.

The following five criteria are the basis for a diagnosis of chronic idiopathic urticaria:

  • Symptoms: There are intensely itchy hives with well-defined, raised wheals. Pain and burning may also be present.
  • Medical history: This is specifically focused on your allergies, contact with foreign substances and occupational hazards, past medical conditions, and any medications you are taking that may be the cause of your urticaria, therefore ruling out CIU.
  • Physical examination
  • Duration: You have had symptoms for six or more weeks.
  • No specific or identifiable cause


CIU is generally not life-threatening and may resolve on its own without treatment. In fact, most cases resolve within a year.

Chronic hives can cause significant discomfort, greatly affecting one's quality of life, so medication is often taken to lessen the severity and duration of your symptoms.

Histamine receptor blockers, namely second-generation H1 antihistamines, are the mainstay of treatment. Examples of common over-the-counter (OTC) second-generation H1 blockers that treat CIU include:

These oral OTC tablets should be taken under the guidance of a healthcare provider. The best dose for you will be based on your overall health status. Your healthcare provider will recommend the lowest, most effective dose possible. If your symptoms aren't improving, a higher dose may be tried, or a different medication may be used.

Alternative medications and their drug class include:


Chronic idiopathic urticaria (CIU) is the persistent, often daily appearance of hives (urticaria) that last for six or more weeks for no known reason. It is diagnosed after eliminating possible causes of chronic hives. CIU is treated with antihistamines and other medications if those don't help.

A Word From Verywell 

CIU is a hard-to-diagnose, non-infectious condition that is not life-threatening but may greatly impact your quality of life. Consulting an allergist or dermatologist may help you formulate a treatment plan that provides you with the most relief from your symptoms.

Even if you receive a diagnosis of CIU and have grown accustomed to recurrent outbreaks, you may want to check in with your healthcare provider during acute episodes. The sudden appearance of hives on your body may be an early sign of a severe allergic reaction (anaphylaxis), a medical emergency that requires immediate medical attention. 

Frequently Asked Questions

  • Is CIU an autoimmune disease?

    CIU seems to be an immune-related condition triggered by changes to your gut microbiome. What's more, the presence of autoantibodies (immune proteins that attack your own tissues) against the high-affinity immunoglobulin E (IgE) receptors in about half of people with CIU also supports an autoimmune theory.

  • Will CIU ever go away?

    CIU is generally not life-threatening and may resolve on its own without treatment. Most cases resolve within a year.

  • What can trigger CIU?

    Some studies have pointed to immune dysregulation and alterations in your gut microbiome as possible triggers of CIU, but the exact triggers of the condition are unknown. 

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Kocatürk E, Grattan C. Is chronic urticaria more than skin deep? Clin Transl Allergy. 2019;9:48. doi:10.1186/s13601-019-0287-2

  2. Zhang X, Zhang J, Chu Z, et al. Gut microbiome alterations and functional prediction in chronic spontaneous urticaria patients. J Microbiol Biotechnol. 2021;31(5):747-755. doi:10.4014/jmb.2012.12022

  3. Schaefer, P. Acute and chronic urticaria: evaluation and treatment. Am Fam Physician. 2017;95(11):717-724.

  4. Fraser K, Robertson L. Chronic urticaria and autoimmunity. Skin Therapy Lett. 2013;18(7):5-9.

By Shamard Charles, MD, MPH
Shamard Charles, MD, MPH is a public health physician and journalist. He has held positions with major news networks like NBC reporting on health policy, public health initiatives, diversity in medicine, and new developments in health care research and medical treatments.