Boron Nitride

Boron nitride is an inert, insoluble cosmetic powder used mainly for slip, blurring, and oil-absorption in makeup and some skincare, typically at low-to-moderate percentages, and it is generally well-tolerated in patch testing. Irritation potential is usually limited to mechanical/frictional effects in very reactive or barrier-impaired skin (or ocular irritation if it migrates into the eyes) rather than true chemical irritation. Given rare reports of sensitivity and the reality of compromised-skin populations, I score it as very gentle rather than completely inert. Safety Notes: In real-world consumer skincare and hybrid skincare-makeup products, boron nitride is often used at very low levels (~0.05–0.5%) in lotions/serums/primers to add slip and reduce tack, while many face powders/blur primers and silicone-heavy leave-on products commonly sit around 1–8%. The highest OTC levels are seen in anhydrous powders, stick balms, and putty/blur primers where boron nitride can function as a primary texture/soft-focus filler, reaching about 10–20% in some consumer-available products. It is overwhelmingly a leave-on cosmetic/personal care ingredient; rinse-off usage exists but typically remains at the low end because sensorial benefits are less persistent.