10 Common Allergy Triggers Slideshow Pictures Take the Quiz on Allergies Nasal Allergy Relief Slideshow Pictures

Medical Author:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Hives and Angioedema Causes

Hives and angioedema are reactions of the skin to histamine and other chemicals such as bradykinin, leukotriene C4, and prostaglandin D2. These chemicals act on blood vessels and other tissues to produce the clinical signs of hives and angioedema. This process is often, although not always, due to an allergic reaction.

• There are many causes of hives and angioedema. At least half the time, the specific cause cannot be determined. When the cause of a medical condition is not known, it is termed idiopathic. Idiopathic hives and angioedema are very common.



• Some of the more common triggers include the following:



• Infections such as viral illnesses, especially in children



• Allergies to food, medications, cosmetics, soaps, and detergents



• Insect stings and bites



• Transfusions of blood or blood products



• Emotional and physical stress



• Physical agents such as sunlight, heat, cold, water, or pressure



• Exercise



• Allergies to pet dander



• Chronic hives are hives that lasts longer than six weeks. This can happen to anyone, but it is most common in women who are 40-60 years of age. Chronic hives can last for months or even years, but this is unusual.



• Risk factors for hives and angioedema include the following:



• A previous case of hives or angioedema



• A previous allergic reaction



• Family members who have hives or angioedema