Nicotinamide (nicotinamide; niacinamide), also known as nicotinamide, is the amide compound of niacin.  White crystalline powder; odorless or almost odorless, bitter taste; slightly hygroscopic. It is easily soluble in water or ethanol, and soluble in glycerol. Clinically, it is mainly used to prevent and treat pellagra, stomatitis, glossitis, sick sinus syndrome, and atrioventricular block.
niacinamide lighten skin：
Our skin is like a wall, blocking the environment and cells, that is to say preventing the entry of chemical molecules and microorganisms in the environment. As can be seen from the figure below, the melanocytes that can produce melanin particles are at the bottom of the epidermis.
On the one hand, nicotinamide can interfere with the cell signal channel between keratinocytes and melanocytes, reducing melanogenesis. On the other hand, it can also act on the melanin that has been produced, reducing its transfer to surface cells.
Niacinamide acts on the surface of the skin. Although it has no direct whitening effect, it has a good moisturizing effect. After increasing the water content of the stratum corneum, the skin will look smoother and brighter. Simply put, niacinamide can prevent melanin from reaching the surface of the skin.
It should be noted that when some people use niacinamide, they may experience redness, hotness and even long mouth closure, because the niacin in niacinamide is easy to irritate the skin. For the skin, the concentration is less than 5%. Relatively safer, the formula of nicotinamide is best to control the pH between 5~7.