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