Silica

Silica (typically amorphous, used as an absorbent, anti-caking/texture agent in leave-on products and makeup) is generally well-tolerated at common use levels, with low rates of positive patch-test reactions. Irritation is uncommon but can occur in very reactive or barrier-compromised skin due to its oil-absorbing, mattifying effect increasing dryness and friction, so it is best rated as very gentle rather than inert for high-sensitivity populations. Safety Notes: In commercial skincare and makeup, silica (including amorphous silica, silica silylate, and microspheres) is used at very low levels (~0.05–0.5%) as a flow/anti-caking aid or minor sensory modifier in emulsions and cleansers, and more typically ~1–8% for oil-absorption, blurring, and slip in primers, sunscreens, and lotions. The highest consumer-available levels are found in anhydrous setting powders, blur powders, and some “silica microsphere” oil-control powders where silica can be a primary bulking/absorbing phase, reaching ~20–40% depending on the powder base (leave-on powders and primers trend higher than rinse-off products). Regulatory frameworks (EU/FDA) generally permit silica as used in cosmetics, with practical limits driven by aesthetics, dustiness/respiratory considerations for loose powders, and stability/viscosity in leave-on emulsions rather than a specific numeric maximum.