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NEED TO KNOW
Acute urticaria lasts less than six weeks , with the most common cause being transient infection .
— In the smaller proportion of acute urticarias caused by IgE-mediated allergic reactions , thorough history and selective allergy testing confirm the diagnosis .
Chronic urticaria — defined as urticaria occurring at least 2-3 days a week for more than six weeks — has a debilitating impact on quality of life .
Several treatment options are available .
— Second-generation antihistamines are effective in most cases . Antihistamines are safely used in higher-than-standard doses for urticaria .
Refer patients who fail to respond to high-dose antihistamine for consideration of effective newer therapies , including omalizumab , which is accessible via the PBS .
Chronic inducible urticaria is a subgroup of chronic urticaria precipitated by physical triggers , such as heat , cold and exercise .
In patients with angioedema without weals , consider non-histaminergic differentials , such as hereditary angioedema , drug-induced angioedema ( commonly ACEI associated ) and acquired angioedema .

Urticaria in adults

Dr Joshua Jacob ( left ) Immunology advanced trainee , Campbelltown Hospital ; clinical lecturer , University of Sydney , Sydney , NSW .
Professor Constance H
Katelaris ( right ) Head of unit and senior staff specialist , Campbelltown Hospital ; professor of immunology and allergy , Western Sydney University , Sydney , NSW .
Copyright © 2023 Australian Doctor All rights reserved . No part of this publication may be reproduced , distributed or transmitted in any form or by any means without the prior written permission of the publisher . For permission requests , email : howtotreat @ adg . com . au
This information was correct at the time of publication : 3 November 2023
BACKGROUND
URTICARIA is a skin eruption characterised
by erythematous superficially oedematous plaque lesions , described as weals . The weals are variable in size and are surrounded by areas of reflex erythema , known as a flare response .
Urticaria can affect any skin or mucous membrane site because it is driven by activation of mast cells . Affected skin returns to normal without scarring typically within 30 minutes to 24 hours . 1 In some patients , the skin eruption is also associated with angioedema . In a smaller proportion of cases , patients present with angioedema in the absence of visible weals .
Urticaria can be divided into three clinical phenotypes : acute , chronic inducible and chronic spontaneous .
Acute urticaria is very common , with an estimated lifetime prevalence of up to 20 %. 2 Patients are often extremely distressed with skin irritation and fear of a sinister cause . Acute urticaria is typically self-limiting and can be managed with simple oral antihistamine therapy .
Chronic urticaria is a highly impactful and debilitating condition , with patients experiencing severe pruritis and reduced quality of life . 3 The condition is commonly trivialised , and its distressing impact may be under-recognised . The unpredictability of episodes is associated with interrupted sleep , low mood , anxiety and poor performance in daily function . There is associated significant economic burden , including direct costs of medicines and indirect costs in lost productivity . 4 , 5
Chronic spontaneous urticaria refers to relapsing urticaria , which may or may not be associated with angioedema . It also describes cases that present with histaminergic angioedema without associated weals . No clear trigger for episodes of urticaria is present in this phenotype . Although some patients experience spontaneous remission within one year , many cases can persist for longer than five years , resulting in a significant impact on quality of life .
Chronic inducible urticaria ( CIndU ) is characterised by weals and / or angioedema that are induced by
specific physical or environmental stimuli . CIndU manifests with a spectrum of severity — from mild simple dermographism to severe urticaria and anaphylaxis triggered by exposure to cold temperatures .
This How to Treat discusses the epidemiology , pathogenesis , diagnosis and management of urticaria in adults and aims to ensure GPs are comfortable assessing and managing urticaria in partnership with immunologists .
CLASSIFICATION AND TERMINOLOGY
INTERNATIONAL guidelines suggest
classifying urticaria based on duration , into acute ( lasting less than six weeks ) and chronic ( persisting longer than six weeks ). 2 Chronic urticaria is divided into spontaneous or inducible ( see box 1 ), depending on whether eliciting factors are present . CIndU may be divided into physical ( for example , dermographism , cold ) and non-physical ( for example , cholinergic , aquagenic ). However , the authors favour classifying these groups together as CIndU . Current
Box 1 . Aetiology of urticaria
• Acute urticaria ( less than six weeks ): — Acute spontaneous . — Infection ( bacterial , viral , parasitic , fungal ).
• Chronic urticaria ( longer than six weeks ): — Chronic spontaneous . — Chronic inducible :
• Dermographism .
• Cholinergic .
• Cold induced .
• Heat induced .
• Solar .
• Vibratory .
• Delayed pressure .
• Aquagenic .
Source : Zuberbier T et al 2022 2 , Schaefer P 2017 8
guidelines suggest that differential diagnoses , such as urticarial vasculitis and cutaneous mastocytosis , be classified separately ( see box 2 ) as their underlying pathomechanisms differ significantly from true urticaria . 2 , 6