Hives are small, itchy, red swollen areas on the skin. The swelling occurs singularly or in clusters. Hives tend to fade after a few hours, but new ones can appear. Most cases go away within a few days. However, some last a few weeks or longer.
Hives are often caused when the body releases a chemical called histamine. Histamine is released during an allergic reaction. Many people, though, get hives without being exposed to something they are allergic to.
While the cause is unknown in some cases, these factors may cause hives:
Allergic skin conditions. American Academy of Allergy, Asthma & Immunology website. Available at: http://www.aaaai.org/conditions-and-treatments/library/at-a-glance/allergic-skin-conditions. Updated October 2, 2017.
Dibbern DA Jr. Urticaria: selected highlights and recent advances. Med Clin North Am. 2006;90(1):187-209.
Gambichler T, Breuckmann F, Boms S, Altmeyer P, Kreuter A. Narrowband UVB phototherapy in skin conditions beyond psoriasis. J Am Acad Dermatol. 2005;52(4):660-670.
Guldbakke KK, Khachemoune A. Etiology, classification, and treatment of urticaria. Cutis. 2007;79(1):41-49.
Hives. American Academy of Dermatology website. Available at: https://www.aad.org/public/diseases/itchy-skin/hives. Accessed October 2, 2017.
Kaplan Allen P. Chronic urticaria: pathogenesis and treatment. J Allergy Clin Immunol. 2004;114(3): 465-474.
Last reviewed September 2018 by
EBSCO Medical Review Board
Marcin Chwistek, MD
Last Updated: 9/30/2014
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