In general, injections are done using a clean, sterile technique: wash hands, clean the skin with an alcohol prep, let it dry fully, and avoid touching the cleaned area before injecting
Available from: Houmard JA
Chen B, Guo K, Zhao X, Liu Z, Xu C, Zhao N, Xu F J
Functional diversity of cysteine residues in proteins and unique features of catalytic redox-active cysteines in thiol oxidoreductases
Without oxidative stress, cysteine and cystine appear to essentially mediate cellular stress via thiols other than GSH (Rahman and MacNee, 2000
Your GP surgery were wrong to stop treatment that has been effective for two decades, and wrong to ignore medical evidence from the Schilling Test, and wrong to ignore guidelines from the British Committee for Standards in Haematology - and wrongly interpreting two negative IFab test results as conclusive evidence that you do not have PA