First, the skin itches, then it erupts into red welts. The itching may be severe, keeping people from working or sleeping. It's a distressing disorder that affects an estimated 20 percent of the population at one time or another in their lives. Commonly known as hives, urticaria has two forms: most cases are acute (lasting from a few hours to less than six weeks); some are chronic (lasting more than six weeks). The welts may appear in one place, disappear after a short time, and then erupt in another area. They are made worse by scratching. Each individual hive lasts no more than 24 hours.
What kinds of things can trigger attacks of urticaria?
Bouts of urticaria have been traced to such triggers as certain foods and additives, infections, drugs (including antibiotics, aspirin, ibuprofen), cold, sun exposure, insect stings, alcohol, exercise, endocrine disorders (thyroid disease) and emotional stress. In some people, pressure caused by belts and constricting clothing causes the eruption. Urticaria may be a response to infection, including the common cold, strep throat, and infectious mononucleosis. In the urticaria-prone person, these triggers cause the body to release chemical mediators, including histamine, from cells. Histamine (which causes itchy, runny noses, and watery eyes in hay fever sufferers) dilates the walls of blood vessels, allowing fluids to leak out into the surrounding tissues. Swelling and itching are the results.
While hives develop on the skin's surface, angioedema is a swelling of the deeper layers of the skin. It most often occurs on the hands, feet, and face. If the angioedema occurs in the throat, normal breathing or swallowing can be blocked, and emergency measures must be taken. Hives and angioedema may appear together or separately on the body. Angioedema usually lasts one or two days but may reoccur with or without hives over an indefinite period of time.
How are each person's urticaria "triggers" identified?
In some cases, the trigger is obvious - a person eats peanuts or shrimp, then develops urticaria within a short time. But because there are so many possible causes for urticaria, other cases require careful detective work on the part of the physician and, sometimes, forbearance on the part of the patient.
To unravel the urticaria puzzle, your allergist will take a detailed history, looking for clues in your lifestyle that will help pinpoint the cause. You'll be asked about the frequency and severity of your symptoms, your family's history, medications you are taking, your work and home environment, and miscellaneous matters. In some cases, you may require tests to analyze blood and urine, and other procedures such as x-rays. Although skin tests are not routinely performed, they may provide useful information in some cases. Your allergist will decide which tests to order based on the different types of urticaria and the suspected cause.
What are the different types of hives/urticaria?
There are two major categories - Immunologic and Non-Immunologic.
Allergic or Immunologic Urticaria is the least common form. It is caused by the immune system's overreaction to foods, drugs, infection, insect stings, blood transfusions, or other substances. Foods such as eggs, nuts and shellfish, and drugs such as penicillin and sulfa are common causes of allergic or immunologic urticaria.
Non-Immunologic Urticarias are those types of urticaria where a clear-cut allergic basis cannot be proven. These take many forms.
Dermographism is a common form of urticaria, which occurs in approximately 8-10% of the population. It develops when the skin is stroked with a firm object, and often occurs after scratching, or when tight-fitting clothes rub the skin
Cold-Induced Urticaria appears after a person is exposed to low temperatures - for example, after a plunge into a swimming pool or when an ice cube is placed against the skin. Coldwater or liquids can provoke symptoms on the lips or in the mouth
Cholinergic urticaria is the term for hives that can develop after activities that increase the body's temperature. Activities that can cause this include a warm bath, shower, jacuzzi, exercise, a fever, or emotional stress.
Solar Urticaria arises on parts of the body exposed to the sun; this may occur within a few minutes.
Exercise is another cause of hives. Some individuals can also have more severe reactions, including wheezing and/or drop of blood pressure, with loss of consciousness. Such a severe reaction is called exercise-induced anaphylaxis.
Other: Some cases of non-immunologic urticaria may be caused by non-allergic reactions to various non-steroidal anti-inflammatory drugs (aspirin, ibuprofen) and, possibly, certain food dyes, sulfites, and other food additives.
Idiopathic Urticaria: In many cases, particularly in chronic urticaria, the trigger for the problem can't be found; in this instance, it is called Idiopathic Urticaria.
How is urticaria treated?
Your allergist first will alleviate the discomfort with medications such as antihistamines. Severe attacks may require injections of epinephrine. In some cases, corticosteroids such as prednisone may be prescribed for a short period. Other drugs may be required for specific types of urticaria. Of course, if the cause can be identified, the best course of treatment is the avoidance of the offending substance. If a specific food is strongly suspected, then it should be avoided. This may require careful reading of food labels and inquiries about ingredients in restaurant meals. Persons with solar urticaria should wear protective clothing and apply sunscreen when outdoors. Loose-fitting clothing will help relieve pressure urticaria. Avoid harsh soaps and frequent bathing to reduce the problem of dry skin, which can cause itching and scratching that can aggravate urticaria. Vigorous toweling after a bath may precipitate hives. Although the success of identifying the cause of chronic urticaria varies from clinic to clinic according to patient populations, it usually is no higher than 20-40% of cases. It may last for months or years and usually burns itself out, never to bother the sufferer again.
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