Hives (urticaria) and swelling (angioedema) are very common: nearly 20% of the population suffers from hives at some time in life. Estimates have been even higher in some studies, with 40% of patients having hives alone, and almost 50% having both hives and swelling. Hives lasting 2-4 weeks or less are called acute, and are more frequent in children, whereas chronic or recurrent hives lasting more than six weeks are more common in adults. Since hives are very common and easy to recognize, patients often make the correct diagnosis and treat themselves. It is important, however, to see your physician in cases of chronic or recurrent hives, so that a more serious, underlying condition is not missed.
What causes hives? First of all, hives are raised, circular or oval shaped areas that vary in size from very small to large, and may appear alone or as multiple lesions. Individual lesions seldom last longer than 24-48 hours; although new lesions commonly arise as older ones fade away. Of particular significance is that hives almost always itch (pruritus). In cases of swelling, since swelling develops in the subcutaneous tissues where there are fewer sensory nerve endings, little or no itching occurs. Swelling is especially likely to develop in areas such as the eyelids and lips. Both hives and swelling can be asymmetrical; that is, occurring on only one side of the body.
Research has now shown that “idiopathic” hives; that is, hives without a known cause, accounts for 75% of all patients, and much like allergies or asthma, is a chronic inflammatory disease. Research has also shown that an antibody called IgE, which is made in the tissue, can bind to tissue mast cells and cause the release of chemical inflammatory “mediators”. These mediators work in the tissue to cause hives and swelling.
One is more likely to find a cause for acute rather than chronic, recurrent hives and swelling. In some instances, the appearance of the lesions gives a clue. For example, lesions limited to exposed areas suggest sun-induced or cold-induced urticaria. The most common causes include: medications, foods and additives, infection, stress, inhalants, bites and stings, contact, autoimmune disease (i.e., lupus, hypothyroidism), physical factors (i.e., cold, pressure, heat, and light), cancer and genetics.
How do we diagnose hives and swelling? For cases of chronic, recurrent hives, a good history and physical examination are always performed, and specific laboratory tests to exclude important underlying causes are reasonable and appropriate. Since in many cases a specific cause is unlikely to be found, it is best to control the lesions until they “burn out” and remission occurs. Antihistamines alone or in combinations may relieve itching and decrease the incidence of severity of hives and swelling. Treatment may be needed for months or until symptoms fully resolve. Severe cases may need to be treated for a short period with oral corticosteroids (i.e. prednisone). The point to remember is that active research is ongoing, and that patients with chronic hives can still live comfortable, full lives with proper diagnosis and treatment.