Flushing with Niacin

Flushing after Niacin oral intake is a microvascular dilation induced by prostaglandins. It is dose-dependent. There is no argument for its "beneficial" effect. Simply the more niacin you absorb the more PG you synthesize in a short period of time. In a prospective reasoning, it would be preferable that the vasodilation effect would be weaker end last longer.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2779993/