WHAT IS CSU?
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what is csu?

If you’ve been dealing with recurring hives or swelling, it’s normal to feel confused or frustrated.

Overview

Chronic Spontaneous Urticaria (CSU) is a chronic skin condition marked by recurring hives and/or swelling lasting six weeks or more, often without a clear trigger. 1, 2, 3

Symptoms are unpredictable and not always visible, which can delay recognition and underestimate their impact on daily life. 4, 5

Symptoms appear

Day 1

Symptoms appear

Hives

Symptoms fade

Day 2

Symptoms fade

You think it's resolved

Symptoms return

Day 3

Symptoms return

A recurring pattern begins

Illustrative example only. Every patient’s experience with CSU is different, and symptoms timing and recurrence can vary.

~50% of patients continue to experience unpredictable and distressing symptoms despite taking the recommended dose of antihistamine medicines. 6, 7, 8

Key facts

Key facts

  • CSU can be difficult to recognise early, leading to delays in diagnosis or misdiagnosis9
    Unlike some other forms of hives, CSU is not always triggered by allergens. It involves inappropriate activation of the immune system,10 leading to unpredictable flare-ups of itch, hives and swelling.
  • Sleep is heavily affected
    3 in 5 people with CSU struggle with sleep.11
  • The patient-doctor gap
    Almost 1 in 3 patients report symptoms that feel more severe than their doctor perceives.3

Symptoms

CSU symptoms are similar to short-lived hives, but they recur frequently and persist over time. Symptoms typically appear at least twice a week and can continue for six weeks or longer.12

Common signs include:

Raised, itchy bumps (hives)

Raised, itchy bumps (hives)

that may be red or skin-coloured12

Hives that “blanch”

Hives that “blanch”

(turn white in the centre) when pressed12

May or may not

May or may not

be accompanied by a sudden, pronounced swelling (angioedema)13

Recurring

Recurring

without a clear cause or identifiable trigger13

Lasting for six weeks or longer

Lasting for six weeks or longer

sometimes months or years13

Ask For More

Diagnosis can take time

Symptoms appear

Symptoms appear

They disappear and return

They disappear and return

Diagnosis is delayed

Diagnosis is delayed

CSU can be difficult to recognise early because symptoms come and go and are not always visible.
This can delay diagnosis for some patients.9

CSU is diagnosed after ruling out other conditions with similar symptoms, a process known as diagnosis of exclusion.13

What helps at medical appointments

If symptoms aren’t visible on the day of your visit, these can help your doctor understand what’s happening:

  • Photos of flare-ups
  • A timeline of when your symptoms started, how often they return, and how long they last can give your doctor a fuller picture
  • Notes on how symptoms affect sleep, daily activities, work, or social life
What helps at medical appointments

What to expect after diagnosis

You might want to explore:

Why some people still feel “unwell”

Why some people still feel “unwell”

~50% of patients continue to experience unpredictable and distressing symptoms despite taking the recommended dose of antihistamine medicines.6, 7, 8

What good control looks like

What good control looks like

Be clear about your treatment goals and discuss them with your doctor. Your goal doesn’t have to be “slightly better”. It’s reasonable to aim for minimal symptoms and little disruption to daily life.

If you're still having persistent hives and itch, losing sleep, or planning life around flare-ups, it is reasonable to Ask For More.

SOURCES

  1. Fricke J, Ávila G, Keller T, Weller K, Lau S, Maurer M, Zuberbier T, Keil T. Prevalence of chronic urticaria in children and adults across the globe: Systematic review with meta-analysis. Allergy. 2020 Feb;75(2):423-432. doi: 10.1111/all.14037
  2. Weller K, Winders TA, McCarthy J, Saraswat P, Chapman-Rothe N, Raftery T, Bernstein JA. The Urticaria Voices Study: Physicians’ Perspectives on the Real-World Patient Burden, Treatments, and Outcomes in Chronic Spontaneous Urticaria. Dermatol Ther (Heidelb). 2025;15:2925–2946. doi:https://doi.org/10.1007/s13555-025-01498-9
  3. Mosnaim G, Patil D, Kuruvilla M, Hetherington J, Keal A, Mehlis S. Patient and physician perspectives on disease burden in chronic spontaneous urticaria: A real-world US survey. Ann Allergy Asthma Immunol. 2025 Mar;134(3):315-323.e3. doi: 10.1016/j.anai.2024.11.028
  4. Balp MM, Khalil S, Tian H, Gabriel S, Vietri J, Zuberbier T. Burden of chronic urticaria relative to psoriasis in five European countries. J Eur Acad Dermatol Venereol. 2018 Feb;32(2):282-290. doi:10.1111/jdv.14584
  5. Zuberbier T, Ensina LF, Giménez-Arnau A, Grattan C, Kocatürk E, Kulthanan K, Kolkhir P, Maurer M. Chronic urticaria: unmet needs, emerging drugs, and new perspectives on personalised treatment. The Lancet. 2024 July;404(10450):393-404. doi: 10.1016/S0140-6736(24)00852-3
  6. Kolkhir P, et al. Poster presented at: 33rd EADV Congress; September 25-28, 2024; Amsterdam, Netherlands. Poster P3627
  7. Laires PA, et al. Poster presented at: EAACI Congress 2023; Jun 9-11, 2023; Hamburg, Germany. Poster TP-C105
  8. Maurer M, Abuzakouk M, Bérard F, et al. The burden of chronic spontaneous urticaria is substantial: Real-world evidence from ASSURE-CSU. Allergy. 2017 Dec;72(12):2005-2016. doi: 10.1111/all.13209
  9. Friedman A, Kwatra SG, Yosipovitch G. A practical approach to diagnosing and managing chronic spontaneous urticaria. Dermatol Ther (Heidelb). 2024 Jun;14(6):1371-1387. doi: 10.1007/s13555-024-01173-5
  10. Powell RJ, Leech SC, Till S, Huber PA, Nasser SM, Clark AT; British Society for Allergy and Clinical Immunology. BSACI guideline for the management of chronic urticaria and angioedema. Clin Exp Allergy. 2015 Mar;45(3):547-65. doi: 10.1111/cea.12494
  11. Weller K, Winders T, McCarthy J, Raftery T, Saraswat P, Constantinescu C, Balp MM, Bernstein JA. Urticaria Voices: Real-World Experience of Patients Living with Chronic Spontaneous Urticaria. Dermatol Ther (Heidelb). 2025 Mar;15(3):747-761. doi: 10.1007/s13555-025-01348-8. Epub 2025 Feb 28. PMID: 40019716; PMCID: PMC11909366.
  12. American College of Allergy, Asthma & Immunology. Chronic Spontaneous/Idiopathic Urticaria (Chronic hives). Available at: https://acaai.org/allergies/allergic-conditions/skin-allergy/chronic-hives/ [Last accessed:  February, 2026]
  13. Zuberbier T, Ansari ZAH, Abdul Latiff AH, et al. The international guideline for the definition, classification, diagnosis and management of urticaria. Allergy. 2026;1-51. doi: 10.1111/all.70210