Chronic spontaneous urticaria (CSU) – also known as chronic idiopathic urticaria – is a condition characterised by the recurrent appearance of hives (wheals), angioedema (swelling beneath the skin), or both, without an identifiable external trigger.

"Spontaneous" means the hives occur without a consistent cause such as food, insect sting, or physical stimulus. "Chronic" means symptoms persist for six weeks or longer.

Hives appear as raised, itchy, red or skin-coloured welts that can occur anywhere on the body. Angioedema causes deeper swelling, typically of the lips, eyes, throat, hands, or feet.

CSU is not life-threatening in most cases, but significantly impacts quality of life and daily function, often causing sleep disturbance, anxiety, and interference with work and social activities.

How common is Chronic Spontaneous Urticaria?

CSU affects approximately 0.5–1% of the global population at any given time, with up to 20% of people experiencing hives at some point in their lives. CSU is most commonly diagnosed in adults between the ages of 20 and 40 and affects women approximately twice as often as men.

The condition typically lasts one to five years, though some people experience it for much longer. In Australia, CSU is a recognised chronic condition managed primarily by dermatologists and allergists.

Symptoms occur daily or nearly daily for six weeks or more by definition.

These include:

• • Hives (wheals) – raised, itchy, red or pale welts of varying sizes that typically resolve within 24 hours but recur elsewhere
  • Intense itch (pruritus) – often the most distressing symptom; can be severe and disruptive to sleep
  • Angioedema – swelling beneath the skin surface, typically around the eyes, lips, throat, hands, genitals, or feet; usually resolves within 72 hours
  • Burning or stinging sensation of the skin
  • General symptoms including fatigue, mood disturbance, and reduced quality of life during active periods

Angioedema involving the throat or airway is rare in CSU but requires urgent emergency medical attention.

In most people with CSU, no specific trigger is identified, hence "spontaneous".

However, several mechanisms are understood:

• • Autoimmune activation – in around 30–50% of people with CSU, autoantibodies (particularly anti-IgE or anti-FcεRI antibodies) activate mast cells and basophils, triggering histamine release
  • Mast cell dysregulation – abnormal activation or sensitivity of mast cells in the skin leads to histamine and other inflammatory mediator release
  • Infection – some cases are associated with bacterial (H. pylori), viral, or parasitic infections; treating the infection can improve or resolve CSU in some patients
  • Thyroid autoimmunity – an association between CSU and autoimmune thyroid disease is recognised, though the mechanism is unclear

Stress may worsen symptoms but is not considered a direct cause.

CSU is a clinical diagnosis made by a doctor – typically a dermatologist or allergist – based on history and examination.

Investigations are used to exclude other causes and identify any treatable underlying condition:

• • Detailed clinical history – duration, frequency, pattern, and any apparent triggers; history of angioedema; previous treatments
  • Physical examination – assessment of wheals and any signs of angioedema
  • Basic blood tests – full blood count, ESR/CRP, thyroid function, and thyroid autoantibodies to screen for associated conditions; H. pylori testing where relevant
  • Allergy testing – skin prick testing and specific IgE testing are generally not useful in CSU, as the condition is not IgE-mediated allergen-triggered in the classic sense
  • Urticaria Activity Score (UAS7) – a validated symptom diary tool used to grade severity and guide treatment decisions

Treatment follows a step-up approach guided by symptom severity and response.

• • Antihistamines — Non-sedating second-generation H1-antihistamines (cetirizine, loratadine, fexofenadine) are first-line therapy. Doses up to four times the standard dose may be used under specialist guidance in refractory cases.
  • Omalizumab (Xolair) — For patients with inadequate response to high-dose antihistamines, omalizumab (Xolair) is an anti-IgE monoclonal antibody used as the next step. It significantly reduces hive activity and itch in most patients and is administered as a subcutaneous injection every four weeks.
  • Cyclosporin — Cyclosporin (Sandimmun) is sometimes used as an immunosuppressant in refractory CSU where omalizumab is unavailable, not tolerated, or not effective. It requires close monitoring due to its side effect profile.
  • Corticosteroid — Short courses of oral corticosteroids may be used to manage severe acute flares but are not suitable for long-term use due to significant side effects.

The following specialty medications may be available at Ace, a specialty pharmacy for Chronic Spontaneous Urticaria.

With Ace, you’ll benefit from:

• • Expert Support — Our dedicated team of health concierges is always available to answer your questions, provide guidance, and help you navigate your condition with confidence.
  • Specialty Medication — We offer a wide range of specialty medications and support services, designed specifically for those living with chronic illnesses. Whether you’re looking for help managing a specific condition, or simply need access to the medications you need, we’ve got you covered.
  • A Wide Range of Conditions — From diabetes to heart disease, and everything in between, we help manage a variety of special condition

Take control of your health and well-being, and start your journey to better health with Ace today.

CSU & Skin Condition Support

• • Australasian College of Dermatologists – find a dermatologist and clinical information on skin conditions
  • ASCIA (Australasian Society of Clinical Immunology and Allergy) – Urticaria
  • Eczema Association Australasia – Australian support organisation for skin conditions including urticaria

Clinical Resources

• • Healthdirect – Hives (Urticaria)
  • DermNet – Urticaria – comprehensive clinical dermatology resource