Introduction PARP (Poly ADP Ribose Polymerase) inhibitors are an effective maintenance therapy for various entities, such as BRCA (breast cancer gene) mutated or HRD (homologous recombination deficiency) positive primary platin-sensitive advanced ovarian cancer after platin induction therapy and in relapse after responding to carboplatin reinduction. Other entities are metastatic BRCA mutated pancreas, prostate and Her2-negative breast cancer. Therefore, patients with allergic reactions to PARP inhibitors should undergo a desensitization procedure to be able to receive this efficient therapy. Case report We conducted a two-day desensitization on a 45-year-s old patient with advanced ovarian cancer who displayed symptoms of an allergic reaction to Olaparib. Management and outcome Using an Olaparib tablet suspension, we orally administered increasing Olaparib doses, starting with 12.5 mg and reaching a cumulative dose of 387.5 mg on the first day and starting with 100 mg and reaching a cumulative dose of 600 mg on the second day, without concomitant antiallergic medication. Except for mild erythema on day one receding within the hour, no further allergic reactions appeared during desensitization. The patient has since received 300 mg of Olaparib twice a day without further complications or interruptions. Conclusion Desensitization in a two-day suspension protocol is a safe method that ensures effective maintenance therapy for patients with allergic reactions to PARP inhibitors.