SYSTEMIC REACTIONS TO IMMUNOTHERAPY

Systemic anaphylactic reactions occur in a small percentage of patients receiving allergen immunotherapy. A 1 year study was performed in a large health maintenance organization to determine the incidence of systematic reactions (SR) to allergen immunotherapy. We measured the number of SR that occurred during a 12 months period. A SR data sheet was completed for each reaction, documenting the time of onset, symptoms, treatment, history of asthma or previous reaction, and concentration and type of extract. Twenty-seven thousand eight hundred six injection visits resulted in 143 SR (0. 51%). Forty-five percent of the patients (pts) with SR had a history of prior SR, 50% had a history of asthma, and 36% developed reactions in season. Seventy-two percent of SR started within 30 minutes, although 8% appeared after 2 hours. Fifty-seven percent of SR occurred at concentrations of 1,000-10,000 PNU/cc, 25% at 10-100 PNU/cc, and 17% when both concentrations were given at the same visit. Eighty-three percent of SR were judged to be mild, nonlife threatening reactions, requiring no treatment or anti-histamine therapy only. Seventeen percent were judged to be more severe, requiring treatment with epinephrine, with or without other agents, SR are a small but definite risk of immunotherapy. Most SR are mild, but some may be life threatening. The majority of reactions occur within 30 minutes, but significant reactions may occur after 2 hours. A large percentage of SR occurred in patients with a history of asthma, previous SR, or both.