A - Z Encyclopedia
Understanding Hives
the Basics | Symptoms | Treatments
the Basics
What Are Hives?
Hives, or urticaria, are a common allergic reaction in which a rash or welts appear on the skin. Hives are typically quite itchy and can last just a few minutes or several days before going away. Occasionally, however, these annoying blotches can signal more serious problems, especially when accompanied by symptoms such as difficult breathing.
In angioedema, hives develop beneath the skin and can cause disabling swelling of internal organs, life-threatening blockage of air passages, or severe, uncontrollable intestinal contractions. If the swelling occurs in the throat, it can cause suffocation. Chronic cases of hives that do not itch but are accompanied by abdominal pain or diarrhea may be the result of hereditary angioedema.
People who simultaneously develop hives and such symptoms as fever, nausea, abdominal cramps, and shortness of breath immediately after a bee sting, insect bite, or drug injection are in the throes of anaphylaxis. This severe shock to the immune system requires prompt medical attention. In rare cases, failure to get help quickly can be fatal.
What Causes Hives?
When an allergen invades or irritates your body, it causes your body to unleash chemicals known as histamines. Some people react to a high histamine level by developing the rash we call hives. Common allergens that can provoke hives include certain milk products, fish, and nuts; drugs such as penicillin and aspirin; and various food additives, emulsifiers, flavorings, and preservatives. Extreme cold or heat, stress, and pressure on the skin may induce an attack of hives, as can insect bites, infections such as strep throat in children and hepatitis B in adults, and -- in very rare cases -- blood transfusions.
the Basics | Symptoms | Treatments
