Niacin in cholesterol lowering doses (500-2000 mg per day) causes facial flushes by stimulating biosynthesis of prostaglandin D2 (PGD2), especially in the skin.
Taking 325 mg of aspirin 20-30 minutes prior to taking niacin has also been proven to prevent flushing in 90% of patients, presumably by suppressing prostaglandin synthesis,[REF] but this medication also increases the risk of gastrointestinal bleeding,[REF] though the increased risk is less than 1 percent [REF].