What are hives?
Hives are produced by blood plasma leaking through tiny gaps between the cells lining small vessels in the skin. A natural chemical called histamine is released from mast cells, which lie along the blood vessels in the skin. Allergic reactions, foods, drugs, or other chemicals can cause histamine release.
Hives can vary in size from as small as a pencil eraser to as large as a dinner plate, and they may join together to form larger swellings. When hives are forming, they are usually very itchy; they may also burn or sting. In a July 2009 American Journal Of Clinical Dermatology article, researchers Evangelo Frigas and Miguel Park cited reports that nearly 20 percent of the general population will have at least one episode of hives in their lifetime. Acute hives may last for a few days to weeks. If they last for more than six weeks, they are called chronic hives.
The most common causes of acute hives are foods, drugs, infections, insect bites, and internal diseases. Other causes include physical stimuli, such as pressure, cold, and sunlight.
The best treatment for hives is to find the cause and then eliminate it. Unfortunately, this is not always an easy task. Even if a cause cannot be found, antihistamines are usually prescribed to provide some relief. Antihistamines work best if taken on a regular schedule. It may be necessary to try more than one or use different combinations of antihistamines to find out what works best. In severe cases of hives, an injection of epinephrine (adrenalin) or a cortisone preparation can bring dramatic relief.
In 1927, Sir Thomas Lewis reported the association between wheals and small blood vessel dilation, which later confirmed the importance of histamine as a cause of hives. Years of research showed that in addition to allergy, nonimmunological stimuli can cause hives as well. According to an October 2014 PLoS One article by Mey-Fann Lee et al., 30 to 50 percent of patients with idiopathic chronic hives have autoantibodies in their systems, suggesting that the causes of hives could be multifactorial.
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