Abstract: Recent studies have shown that nicotinamide adenine dinucleotide(NAD)is not only a co-enzyme in cellular oxidation.reduction reactions.but also a substrate for reactions catalyzed by mono (ADP-ribose) transferases,poly (ADP-ribose) polymemses and acetylase,and it play important roles in numerous cellular physiologic functions.Nicotinamide is not only a precursor for the synthesis of NAD,but also an inhibitor of NAD-consuming enzymes.Besides pellagra,nicotinamide has been used to ireat immune bullous diseases,atopic dermatitis,rosacea and aene,and so on.Moreover,nicotinamide has shown a favorable perspective in anti-skin aging and cosmetic dermatology.The safety of topical nicotinamide has been already confirmed.but a forlnal safety evaluation routinely designed for a new drug has not been performed for oral nicotinamide at high dose.