NO! Niacin does not work. Do a google for 'L. Ron Hubbard and Niacin'. He did a study years ago to remove LSD residue to prevent flashbacks. Seems a routine of excersize, niacin and saunas will remove trace residue from toxins like LSD. After a few months of this routine, the toxin residue was removed. Come to find out, it also removed the trace residue from THC and other toxins. IT IS NOT FOR DRUG TESTING. It is for removing trace toxins after months of being clean. But some pot head read the report that niacin and a sauna would remove drug toxins and the myth was born. AGAIN, IT WILL NOT HELP FOR DRUG TESTING. And you're right about the itching and flushing like rash from taking Niacin...it's nasty.
HOpe that helps.
N2