The niacin skin flush response (NSFR) is a physiological reaction that occurs when niacin (vitamin B3) is administered, leading to increased blood flow and a flushing sensation in the skin.

rash, dizziness, and low blood pressure. Very high doses of niacin can cause diarrhea, nausea, and jaundice, a yellowing of the skin and eyes due to liver damage. Though it causes some of the same ...