ABSTRACTBackgroundRapid drug desensitization (RDD) is the cornerstone of managing patients with immediate drug hypersensitivity reactions (IDHR) to antineoplastic drugs in Southern Europe and the United States. As the first in Northern Europe, an allergy treatment program that includes RDD and drug provocation testing (DPT) was implemented for Danish patients with cancer. We report the results of this allergy intervention, the number of successful treatments, the fraction, timing and severity of breakthrough reactions (BTR) and the actual treatment duration of RDD procedures.MethodsThis was a prospective observational study. Patients with IDHRs to antineoplastic drugs referred to the allergy treatment program were included. Patients were followed up until finalization of DPT and/or RDD. RDDs were performed according to one‐bag RDD‐protocols with drug concentrations strictly following manufacturer's instructions and infusion sets primed with flushing fluid. The outcome of DPTs and RDDs were recorded together with detailed information on BTRs and treatment duration of RDD‐procedures.ResultsDuring 28 months, 72 patients were included. With DPT, a safe drug alternative was found for five drugs, hypersensitivity was ruled out for six, and one treatment was discontinued after a positive DPT. RDD was performed in 60 patients. Of 248 initiated RDD procedures, 247 were completed. BTRs were observed in 53% of patients and 27% of RDD‐procedures, with most BTRs being mild to moderate. The treatment duration was below 6 hours in 96% of RDD procedures.ConclusionThe allergy treatment program, which included DPT and one‐bag RDD‐protocols, allowed patients to continue critical antineoplastic treatments despite IDHRs.