Immunologic observations during desensitization and maintenance of clinical tolerance to penicillin.

A nurse anesthetist who had experienced four systemic allergic reactions attributed to penicillin exposure was safely and successfully desensitized to penicillin despite predominantly minor determinant allergy (benzyl penicilloate skin test was positive at 1:100,000 dilution of standard 10 mM solution). Because of unavoidable occupational exposure to penicillin, daily oral doses of penicillin were continued after hospital discharge in an effort to maintain clinical tolerance. Immunologic measurements throughout the long-term desensitization effort provided some evidence that in this patient, drug-induced mast cell desensitization is an ongoing dynamic process that is dose dependent and that skin mast cell reactivity recovers slowly over a period of many weeks after the short-term high-dose desensitization protocol. A dose-dependent state of clinical tolerance to inadvertent penicillin exposure has been safely maintained in this patient for 18 mo.