Urticaria is a skin condition characterised by erythematous, blanching, oedematous, non-painful, pruritic lesions that typically resolve within 24 hours and leave no residual markings.
Angio-oedema is swelling involving the deeper layers of the sub-dermis and occurs in association with urticaria in about 40% of cases. It can also occur in the absence of urticaria.
Acute urticaria lasts less than 6 weeks and is often due to a hypersensitivity reaction to a specific trigger. Underlying viral infections are also a common cause of acute urticaria, particularly in children. Acute urticaria is generally self-limiting.
Chronic urticaria is characterised by daily or near-daily episodes of hives occurring for 6 weeks or more and has a complex aetiology.
Diagnosis of acute and chronic urticaria is based on history and physical examination; diagnosis of chronic urticaria may involve additional laboratory testing, depending on the history.
Referral to a specialist may be appropriate, especially in cases of chronic urticaria.
Antihistamines are the mainstay of therapy for both acute and chronic urticaria. For patients who do not respond to antihistamines, additional treatment options include omalizumab and immunomodulatory medications.
Angio-oedema involving the face or neck can potentially compromise the airway and requires prompt airway management.
Urticaria (also called hives) are erythematous, blanching, oedematous, non-painful, pruritic lesions that typically last less than 24 hours and leave no residual markings upon resolution. Approximately 40% of episodes of urticaria have associated angio-oedema. Angio-oedema is swelling involving the deeper layers of the sub-dermis and can occur in both the acute and chronic setting. Episodes that occur over a period of less than 6 weeks are generally considered acute, can be caused by a specific stimulus, and are self-limiting. Episodes that occur over a period of 6 or more weeks are classified as chronic and appear to be “spontaneous". Chronic urticaria is rarely attributed to a specific stimulus. 
Angio-oedema can also occur in the absence of urticaria and this is separate clinical entity, requiring a different diagnostic approach. Depending on the results of history, physical examination and laboratory investigations, it may be classified as drug-induced angio-oedema, hereditary angio-oedema, or acquired angio-oedema.
Allergy and Clinical Immunology
Rochester Regional Health
Clinical Assistant Professor of Medicine
University of Rochester School of Medicine & Dentistry
SSM is on the speakers' panel and advisory board for Genentech.
Dr S. Shahzad Mustafa would like to gratefully acknowledge Dr Stephen Dreskin, a previous contributor to this monograph. SD declares that he has no competing interests.
Honorary Associate Professor
University of Warwick
FH has attended educational events organised and funded by Almrall and Schering Plough; has received speaker's fee from Steibel, Leo, and Schering Plough; and is an author of references cited in this monograph.
Consultant in Dermatology
University Hospital of South Manchester
Head of Allergy and Training Program Director
Winthrop University Hospital
Associate Professor of Clinical Medicine
SUNY at Stony Brook
LF declares that she has no competing interests.
Professor of Medicine
Department of Internal Medicine
Division of Immunology/Allergy Section
University of Cincinnati
JB is the editor of the Joint Task Force Practice Parameters on Urticaria.
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