Vitamin B12 desensitization and provocation: Ten-year clinical experience

<h2>Abstract</h2><h3>Background</h3> Vitamin B12 is an essential micronutrient and hypersensitivity reactions (HSR) are considered rare. <h3>Objective</h3> To present the characteristics of HSRs to vitamin B12 preparations and to report the outcomes of desensitization and drug provocation tests (DPT) for vitamin B12. <h3>Methods</h3> The retrospective descriptive study included patients who required treatment for vitamin B12 deficiency and were hypersensitive to vitamin B12 or hesitant to use it due to other drug allergies. Low-risk patients based on their index reaction and patients hesitant to use vitamin B12 underwent DPT, while desensitization protocols were performed for patients classified as high-risk. Successful completion defined as the execution of all steps in the desensitization and DPT protocols without any subsequent immediate or delayed reactions. <h3>Results</h3> Among the 44 patients, 28 patients (63.6%) had a history of HSRs following the use of cyanocobalamin. The remaining 16 patients (36.4%) had no prior history of HSR to vitamin B12-containing drugs but were hesitant to use vitamin B12 due to other drug allergies. DPT was performed in 38 patients (86.4%), while desensitization was performed in 6 patients (13.6%). The mean age was 46.34 ± 14.50 years and 32 (72.7%) of them were female. Skin prick tests (SPT) and immediate reading intradermal tests (IDTs) were administered in 20 patients (45.5%). Patch tests were conducted in 8 patients (18.1%) and delayed reading IDTs were performed in 3 (6.8%). All skin test results were negative. A total of 40 challenges were conducted and an immediate-type HSR was observed in 1 challenge (2.5%). Desensitization was performed in 8 cycle and HSR occurred in 1 (12.5%) cycle. <h3>Conclusion</h3> DPT is a reliable procedure that provides the assessment of low-risk patients with vitamin B12 hypersensitivity and prevents unnecessary drug restrictions. Additionally, desensitization protocols enable the continuation of vitamin B12 treatment in high-risk patients.