Nicotinamide (INN, BAN UK[2]) or niacinamide (USAN US) is a form of vitamin B3 found in food and used as a dietary supplement and medication.

[4] As a cream, it is used to treat acne, and has been observed in clinical studies to improve the appearance of aging skin by reducing hyperpigmentation and redness.

[18] Nicotinamide increases the biosynthesis of ceramides in human keratinocytes in vitro and improves the epidermal permeability barrier in vivo.

[20] Nicotinamide has been shown to prevent Cutibacterium acnes-induced activation of toll-like receptor 2, which ultimately results in the down-regulation of pro-inflammatory interleukin-8 production.

[9] The structure of nicotinamide consists of a pyridine ring to which a primary amide group is attached in the meta position.

[26] The hydrolysis of nicotinonitrile is catalysed by the enzyme nitrile hydratase from Rhodococcus rhodochrous J1,[27][28][17] producing 3500 tons per annum of nicotinamide for use in animal feed.

NAD+ and NADP+ are cofactors in a wide variety of enzymatic oxidation-reduction reactions, most notably glycolysis, the citric acid cycle, and the electron transport chain.

Nicotinamide occurs in trace amounts mainly in meat, fish, nuts, and mushrooms, as well as to a lesser extent in some vegetables.

[36] A 2015 trial found nicotinamide to reduce the rate of new nonmelanoma skin cancers and actinic keratoses in a group of people at high risk for the conditions.

[39] Nicotinamide has been investigated for many additional disorders, including treatment of bullous pemphigoid nonmelanoma skin cancers.

[41] There is tentative evidence for a potential role of nicotinamide in treating acne, rosacea, autoimmune blistering disorders, ageing skin, and atopic dermatitis.

[40] Nicotinamide also inhibits poly(ADP-ribose) polymerases (PARP-1), enzymes involved in the rejoining of DNA strand breaks induced by radiation or chemotherapy.