The effects of weekly versus monthly ragweed allergen injections on immunological parameters

The practice of administering injections of allergen extract at weekly intervals until maintenance levels are achieved is well established. However, no objective data exist to determine the optimal frequency of immunotherapy during the first few years after reaching maintenance therapy. Nine patients who had reached maintenance immunotherapy within the preceding year participated in a double-blind, crossover study to compare the effects of weekly versus monthly injections of ragweed antigen. The results were assessed by measurements of skin, nasal and conjunctival sensitivity to ragweed and serum levels of IgG and IgE antibodies specific for ragweed--all obtained at monthly intervals. There was a significant increase (P less than .05) in serum ragweed IgG levels when the subjects were receiving weekly injections as compared to monthly injections. There was also a definite trend toward decreased skin and conjunctival sensitivity to ragweed while receiving weekly injections. These data lend immunologic support to the practice of administering weekly injections during the pollen season in the first few years of allergy immunotherapy.