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What are hives caused from?

Find out what causes hives and how to treat them.

Stress or pressure is a common cause of hives. [©Shutterstock, 2010]
©Shutterstock, 2010
Stress or pressure is a common cause of hives.

Hives are red welts that appear suddenly on your skin. According to the Asthma and Allergy Foundation of America, about 20 percent of people have had hives, so it's not an uncommon condition. Hives usually itch, but they can sting or burn and often vary in shape and size. They can be as small as a pencil eraser or as large as a dinner plate. They can appear on different areas of the body, change sizes, disappear and reappear, all within a few hours.

A breakout can last hours, days, weeks or even months. Because hives are one of the fastest skin diseases to occur and resolve, unless you take a picture of your rash, you may not have any evidence to show your doctor. In such cases, your doctor will rely on your medical history to make a diagnosis. Like most conditions, the first step in dealing with this condition is to understand what causes hives.

Allergies and Hives

Hives, or urticaria, are triggered by numerous sources, which are sometimes elusive and idiopathic. Most commonly, though, they are caused by an allergic reaction. The allergens that cause the reaction can include food (especially eggs, shellfish, nuts or berries), medications (usually antibiotics) or dust and pollen in the air. Upon contact, these allergens cause specialized cells along the skin's blood vessels to release histamine, a chemical, which can trigger blood plasma to leak out, causing the characteristic swelling, or wheal, in the skin.

Over the years, people have reported cases of hives caused by allergies to food additives, such as aspartame, a sweetener. While the United States Food and Drug Administration, has not seen any consistent proof of aspartame's an allergenic qualities, people with the genetic disease phenylketonuria and pregnant women with hyperphenylalanine (high levels of phenylalanine, an essential amino acid, in the blood) have shown adverse reactions to aspartame because they cannot metabolize the phenylalanine contained in aspartame. On the other hand, the FDA has proven that one color additive, FD&C Yellow No. 5 (or tartrazine on medicine labels), may prompt hives in a small number of people.

Other Causes of Hives

Other causes of hives include: scratching your skin, getting a bug bite or an infection, or exposure to heat, pressure, exertion and sunlight. Many people, including some doctors and other health care specialists, believe that stress can cause hives. Stress causes the body to produce more adrenaline and cortisol, leading to a chemical imbalance. Excess hormones produced by this imbalance can lead to an outbreak of hives or exacerbate already existing cases of chronic hives. Avoiding common stress triggers is a good way to stave off an unwelcome outbreak of hives.

Other causes may include your body's response to its own antibodies. In other words, your body has an allergic reaction to itself. This may occur through a reaction to blood transfusions, or due to an immune system disorder, such as lupus. Thyroid disorders, as well as infections, like hepatitis, or even a cold can also trigger hives.

Other Types of Hives

While most hives occur on the surface of the skin, angioedema, which is similar to urticaria, causes swelling to occur beneath the skin. Its visible symptoms consist of deep swelling around the eyes and lips and sometimes of the genitals, hands, and feet. While the swelling itself usually subsides within 24 hours, it generally lingers longer than urticaria. On rare occasion, angioedema of the throat, tongue, or lungs can swell and obstruct the airways and cause life threatening suffocation. Like urticaria, angioedema is usually thought to be caused by an allergic reaction and can occur at the same time as urticaria.

More elusive than the causes of ordinary hives are the causes of chronic hives, or hives lasting more than six weeks or recurring frequently. Only around 10 percent of such cases have easily recognized triggers. The rest are idiopathic, or with no known cause. But while the underlying cause of chronic hives remains unidentifiable and unidentified, like ordinary hives, a combination of antihistamine medications are effective treatments for chronic cases.

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