Intravenous immunoglobulin (IVIG) has been used for many years to treat patients with primary immunodeficiencies. More recently, IVIG has been shown to have anti-inflammatory activity when used at substantially higher concentrations. A number of studies have examined the efficacy of IVIG in allergic diseases. For patients with severe refractory asthma, sinusitis, atopic dermatitis, and urticaria, IVIG offers an alternative therapy with relatively few side-effects. Although the mechanism by which IVIG may attenuate the allergic response is still undetermined, clinical studies have shown that immunoglobulin therapy can decrease serum IgE levels and increase glucocorticoid binding affinity, while in vitro studies have shown that IVIG can decrease T-cell secretion of TH2 cytokines. Further studies are needed to confirm the initial encouraging results seen in allergic patients with severe, resistant disease.