Niacinamide leave-on formulation provides long-lasting protection against bacteria in vivo.

Antimicrobial peptides (AMPs) form a part of the skin's innate immune system. Their primary activity is to provide antimicrobial benefits and hence protect from infections. AMPs that are present on human skin include psoriasin (S100A7), RNase 7, lysozyme, LL-37 and defensins. Niacinamide is a well-known cosmetic ingredient that has been used traditionally for multiple skin benefits. Recent data indicate that niacinamide treatment can boost AMPs in human gut epithelial cells and in neutrophils. Treatment with niacinamide in mice also provided protection from skin infections by enhancing AMPs. In this article, we find that treatment with niacinamide formulation provides long-lasting protection against bacteria, potentially through the activation of an AMP response.