Urticaria, also known as welts, hives, or wheals, is characterized by the appearance of intensely pruritic erythematous plaques.[1]Bernstein JA, Lang DM, Khan DA, et al. The diagnosis and management of acute and chronic urticaria: 2014 update. J Allergy Clin Immunol. 2014 May;133(5):1270-7.
http://www.ncbi.nlm.nih.gov/pubmed/24766875?tool=bestpractice.com
It appears clinically as pruritic, pale, blanching swellings of the superficial dermis that last for up to 24 hours. Lesions may be small, large, giant, oval, or annular.[Figure caption and citation for the preceding image starts]: Acute urticaria: typical whealsFrom the collection of Adam Reich, MD, PhD [Citation ends].
[Figure caption and citation for the preceding image starts]: Typical lesions seen in acute or chronic urticariaFrom the collection of Stephen Dreskin, MD, PhD [Citation ends].
[Figure caption and citation for the preceding image starts]: Urticaria: whealsFrom the collection of Adam Reich, MD, PhD [Citation ends].
Urticaria affects 10% to 25% of the population and can occur in any age group.[2]Guldbakke KK, Khachemoune A. Etiology, classification, and treatment of urticaria. Cutis. 2007 Jan;79(1):41-9.
http://www.ncbi.nlm.nih.gov/pubmed/17330621?tool=bestpractice.com
It is a mast-cell-driven disease. The triggering mechanisms for mast-cell activation in urticaria are not well defined but seem to be multiple and diverse.[3]Zuberbier T, Aberer W, Asero R, et al. The EAACI/GA(2)LEN/EDF/WAO guideline for the definition, classification, diagnosis and management of urticaria. Allergy. 2018 Jul;73(7):1393-414.
https://onlinelibrary.wiley.com/doi/full/10.1111/all.13397
http://www.ncbi.nlm.nih.gov/pubmed/29336054?tool=bestpractice.com
Urticaria is classified according to duration of symptoms:
Acute urticaria: the occurrence of spontaneous wheals, angioedema, or both for 6 weeks or less[2]Guldbakke KK, Khachemoune A. Etiology, classification, and treatment of urticaria. Cutis. 2007 Jan;79(1):41-9.
http://www.ncbi.nlm.nih.gov/pubmed/17330621?tool=bestpractice.com
[3]Zuberbier T, Aberer W, Asero R, et al. The EAACI/GA(2)LEN/EDF/WAO guideline for the definition, classification, diagnosis and management of urticaria. Allergy. 2018 Jul;73(7):1393-414.
https://onlinelibrary.wiley.com/doi/full/10.1111/all.13397
http://www.ncbi.nlm.nih.gov/pubmed/29336054?tool=bestpractice.com
Chronic urticaria: urticaria that has been continuously or intermittently present for >6 weeks.[3]Zuberbier T, Aberer W, Asero R, et al. The EAACI/GA(2)LEN/EDF/WAO guideline for the definition, classification, diagnosis and management of urticaria. Allergy. 2018 Jul;73(7):1393-414.
https://onlinelibrary.wiley.com/doi/full/10.1111/all.13397
http://www.ncbi.nlm.nih.gov/pubmed/29336054?tool=bestpractice.com
Chronic urticaria is classified into 2 subtypes:[3]Zuberbier T, Aberer W, Asero R, et al. The EAACI/GA(2)LEN/EDF/WAO guideline for the definition, classification, diagnosis and management of urticaria. Allergy. 2018 Jul;73(7):1393-414.
https://onlinelibrary.wiley.com/doi/full/10.1111/all.13397
http://www.ncbi.nlm.nih.gov/pubmed/29336054?tool=bestpractice.com
Chronic spontaneous urticaria: spontaneous appearance of wheals, angioedema, or both ≥6 weeks due to known or unknown causes.
Inducible urticaria, for example delayed pressure urticaria, heat urticaria, solar urticaria, symptomatic dermatographism, vibratory angioedema, aquagenic urticaria, cholinergic urticaria, and contact urticaria.
Some people have urticaria that is complicated by angioedema, a swelling of the deeper dermis and tissues (e.g., mucosal surfaces), with laryngeal edema potentially causing respiratory distress and death.[3]Zuberbier T, Aberer W, Asero R, et al. The EAACI/GA(2)LEN/EDF/WAO guideline for the definition, classification, diagnosis and management of urticaria. Allergy. 2018 Jul;73(7):1393-414.
https://onlinelibrary.wiley.com/doi/full/10.1111/all.13397
http://www.ncbi.nlm.nih.gov/pubmed/29336054?tool=bestpractice.com
Angioedema is commonly associated with urticaria and may occur at any age.[4]Katelaris CH, Peake JE. MJA practice essentials 5. Allergy and the skin: eczema and chronic urticaria. Med J Aust. 2006 Nov 6;185(9):517-22.
http://www.mja.com.au/public/issues/185_09_061106/kat10399_fm.html
http://www.ncbi.nlm.nih.gov/pubmed/17137459?tool=bestpractice.com
It may not necessarily be seen at the first urticarial episode, and its risk increases with greater exposure to the allergenic substance.[5]Grattan CEH, Black AK. Urticaria and angioedema. In: Bolognia JL, Jorizzo JL, Rapini RP ed. Dermatology (volume one). London, UK: Mosby; 2003;287-302. Symptoms are typically numbness, pain, or paresthesias.[6]Kwong KY, Maalouf N, Jones CA. Urticaria and angioedema: pathophysiology, diagnosis, and treatment. Pediatr Ann. 1998 Nov;27(11):719-24.
http://www.ncbi.nlm.nih.gov/pubmed/9826877?tool=bestpractice.com
Angioedema without urticaria should prompt further evaluation.[1]Bernstein JA, Lang DM, Khan DA, et al. The diagnosis and management of acute and chronic urticaria: 2014 update. J Allergy Clin Immunol. 2014 May;133(5):1270-7.
http://www.ncbi.nlm.nih.gov/pubmed/24766875?tool=bestpractice.com
[Figure caption and citation for the preceding image starts]: Angio-oedema of the lips in a patient who also has urticariaFrom the collection of Stephen Dreskin, MD, PhD [Citation ends].