Topical Niacinamide Does Not Stimulate Hair Growth Based on the Existing Body of Evidence

In a letter to the editor from March 20, 2020, John E. Oblong and colleagues from The Procter & Gamble Company reviewed literature and presented new data to address the belief that topical niacinamide (Nam) promotes hair growth. They concluded that Nam has a neutral effect on hair growth, citing a clinical study that showed increased hair thickness and density with 0.1% Nam treatment but noting the study's limitations, including the absence of a placebo control. Additionally, their in vitro tests revealed that Nam did not stimulate vascular endothelial growth factor (VEGF) synthesis nor showed significant connections to hair growth-related compounds such as adenosine or minoxidil. Based on these findings, they argued that there is no substantial evidence to support the claim that Nam significantly affects hair growth.