can b12 injections cause itchy skin Excess Vitamin And Histamine Intolerance: A Genetic Link 32 Pictures of Skin Rashes:

Our observation that intracellular NA concentrations did not increase following NNMT inhibition extends previous studies that showed NA concentrations were largely unaffected following NNMT knockdown with either adenovirus[39] or anti-sense oligonucleotides (ASOs).[12] It is possible that significant accumulation of NA in adipocytes (and other tissues) is prevented by rapid conversion of NA to NMN and subsequent NAD + synthesis or transport to the extracellular environment.[27] Importantly, NNMT inhibition potentiated the absolute intracellular concentrations of NAD + and SAM, without altering the levels of NA and SAH in the adipocytes

The NAD rise activates SIRT1 and AMPK unlike precursors (NMN, NR) that add raw material, this is a conservation mechanism: less nicotinamide is wasted

All protocol-level guidance is based on published data and preclinical evidence cited inline

Nonetheless, if you feel unwell after the injection, it's best not to drive or handle heavy machinery