What Causes Hives?

You probably know urticaria -- one of the most common skin conditions -- by its non-medical name, hives.

According to the American College of Allergy, Asthma and Immunology, hives affect about 20% of people at some time in their lives. They are red, raised lesions with a white center. Hives come in various sizes, can occur anywhere on the body and are very itchy. They are not contagious, and they tend to come and go. In rare cases, they can last for years. Let's take a deeper look into hives and how to treat them.

Hives occur when histamine, a chemical in the body, is released under the skin from cells called mast cells. Histamine causes the blood vessels to widen and leak fluid, which results in the swelling in the skin. It is this swelling that forms the hives you see on your skin's surface.

We classify hives by the length of time that you have the rash. Acute hives last for less than six weeks, while chronic hives continue for more than six weeks. The causes of acute hives are usually different than those seen with the chronic type.

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Causes of Hives

What are some of the main causes of acute hives? You can get these from allergic reactions to food, medicines and insect stings. Hives can be seen due to reactions to soaps and detergents, pressure on the skin from a belt or bra strap, heat, cold, exercise or stress. Some people develop a non-itchy swelling in areas they scratch or rub. This is called dermatographism and commonly occurs with other types of hives.

Pollens, dust mites and animal danders, which can trigger nasal allergies and asthma, can also trigger hives. In fact, you can even get hives from viral and bacterial infections. Hives also may be the first symptom of anaphylaxis, a serious, life-threatening reaction that requires immediate medical attention. So, if you have a severe episode of hives and start having other problems like swelling, trouble breathing, wheezing, vomiting, diarrhea or feeling faint, call 911 and get to the nearest emergency room.

Hives may be a sign of underlying chronic disorders such as lupus and thyroid disease. As you can see, there are numerous possibilities that can bring on hives.

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The causes of chronic hives are not as well understood. The good news is that most people with hives do not suffer from the chronic type. Fewer than 1% of people with acute hives progress to chronic hives. Unfortunately, most of the time, no cause is found for chronic hives. We usually call this chronic idiopathic or chronic spontaneous urticaria. This condition is more common in women than men and seen with greater numbers in people between 20 and 40 years of age. It is thought that they may have an autoimmune condition or overactive immune system that leads to the problem. A small percentage of cases of chronic hives have physical causes such as heat, cold or pressure. It 's important to know that allergy does not cause this type of hives.

If you are not sure of the cause of your hives, your allergist will perform an extensive history and physical examination related to the possibilities mentioned above. If these suggest a possible cause or underlying disease, specific lab tests will be ordered. For example, if your history points to a food allergy, then allergy testing for foods would be appropriate.

Treating Hives

Treatment of acute hives involves the avoidance or removal of triggers and the use of a certain group of drugs known as "second-generation antihistamines." These include cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin). These are used to control the hives and itching until the problem clears up. Another group of drugs known as "first-generation antihistamines," including diphenhydramine (Benadryl) can also relieve hives. They may have negative effects like dryness and sleepiness, along with requiring more frequent dosing than the second-generation ones. They are therefore not recommended. Sometimes an "H2 antihistamine" such as famotidine (Pepcid) or ranitidine (Zantac) -- commonly used for gastric reflux disease - is added to the treatment for better control.

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For chronic hives, it is not uncommon to try higher doses of second-generation antihistamines and H2 antihistamines than used for acute hives. In severe cases of chronic hives, a short course of systemic corticosteroids may be used to quickly reduce symptoms, but they should never be used long term due to the many serious side effects. A biologic called omalizumab has proven to be very effective in treating patients with chronic hives who are not responding to routine management. Omalizumab is given by a shot in your allergist's office every four weeks, with most patients having complete clearing of their chronic hives.

If you are suffering with hives, be sure to see a board-certified allergist for evaluation of the cause and relief of this unpleasant and itchy rash.