Niacin (nicotinic acid) is an essential B complex Vitamin (B3), whose deficiency results in the clinical syndrome known as pellagra. Nicotinic acid is converted in the body to nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP), which function as coenzymes for a wide variety of vital oxidation-reduction reactions. Nicotinamide (niacinamide), the active ingredient, is the physiologically active form of niacin and is the chemical form of Vitamin B3 found in virtually all multivitamin products. Though nicotinic acid and nicotinamide are so closely related chemically, they differ somewhat in pharmacological properties. Nicotinic acid products exhibit moderately intense cutaneous vasodilation, resulting frequently in mild headaches and flushing or tingling of the skin, but such reactions have not been observed with nicotinamide. Nicotinic acid has also been used for its effect to lower plasma cholesterol, again a property not shared by nicotinamide.
Nicotinamide has demonstrated beneficial effects on inflammatory acne. It is considered that these effects are related to its significant anti-inflammatory activity.