i have faith in it because ive had many friends somke the day before a drug test take about 2,000 mg of naicin, flush by getting all read and itchy, and not really consume any more than normal fluids (drinking a soda with meals etc..) and pass their test, again i know i dont know for sure if its the niacin but it does seem like it
If you dont know for sure but only think it "seems like it so" then how can you have faith or confidence in it?
Niacin does exactly what you said: It makes you red and itchy. To conclude that niacin was the reason for passing the U/A would be a fallacy of causation. Just because B happened doesnt mean that A caused it.
Nothing but a pure coincidence.