Niacin-induced "flush" involves release of prostaglandin D2 from mast cells and serotonin from platelets: evidence from human cells in vitro and an animal model.

Niacin lowers serum cholesterol, low-density lipoprotein, and triglycerides, and it raises high-density lipoprotein. However, most patients experience cutaneous warmth and vasodilation (flush). Acetylsalicylic acid (ASA) can reduce this flush, presumably by decreasing prostaglandin D(2) (PGD(2)) release from macrophages.