The underlying cause of acute hives is often either very obvious or very obscure, with little middle ground. A particular food exposure or a new medication usually presents a strong clue. In these cases, skin testing or serum testing can confirm the presence of allergy to foods or beta lactam antibiotics. It is also important to remember that acute viral or bacterial infections are often associated with urticaria, which may lead to the erroneous diagnosis of an allergy to antibiotics.

Chronic urticaria – hives lasting more than 6 weeks – is associated with a long list of possible etiologies, and is much more difficult to treat. The history provides the most information as to the possible cause. The size and duration of the hives, and whether angioedema occurs with the hives provide important clues to the underlying etiology. Physical triggers, medications, underlying infections, hormonal abnormalities, contact sensitivities, and malignancies must all be considered in the differential diagnosis. Food allergies, while an important consideration for acute urticaria, are a rare cause of chronic urticaria, but should still be considered.

Until recently, an extensive evaluation of these possible etiologies will yield a specific diagnosis of the cause of hives less than 10% of the time; most patients with chronic hives are labeled as having “Chronic Idiopathic Urticaria.” There is a growing body of evidence that the majority of these patients have underling autoimmune disease. These patients have developed IgG antibodies to either the IgE receptor or to IgE itself. Antithyroid antibodies frequently occur in these patients.

Second-generation H1 antihistamines are the mainstay of treatment for both Acute and Chronic Urticaria, regardless of etiology, although certain antihistamines are more effective in subtypes of hives. As with other conditions requiring the use of antihistamines, care must be taken if you use first-generation H1 antihistamines, since these may impair cognition and cause sedation. Some of the sedation problem may be alleviated by dosing at night, but many patients will suffer from a “hangover effect” the next morning. It is worth trying multiple antihistamines to find which is most effective for a particular patient. H2 blockers and leukotrienne antagonists are frequently employed as adjunctive medications. Glucorticoids may also be used for exacerbations, but should be avoided as long-term agents if possible.

There are a number of exciting studies using steroid-sparing, immunomodulating agents to effect long-term amelioration of chronic, autoimmune urticaria. Patients with positive skin tests to aeroallergens, foods, or autologous serum have the highest success rate on these regimens. These agents appear to be disease-modifying; the majority of patients appear to achieve long-lasting remissions after 3-6 months of therapy.

About The Author
Gary B. Moss M.D
www.allergydocs.net