Hydrated Silica

Hydrated silica is an inorganic absorbent/texture agent and, in oral-care and exfoliating products, commonly functions as an abrasive at a few to double‑digit percent; in leave-on skincare it’s typically lower but still can add friction and dryness. While it is generally low in true chemical irritancy or allergy, clinical experience and patch/usage testing show it can cause stinging or eczema flares in highly reactive or barrier-impaired skin, especially when rubbed (cleansers, scrubs, toothpaste). Given the risk is mechanical/irritation-in-use rather than inertness, I rate it as mild rather than exceptionally gentle. Safety Notes: In real-world consumer products, hydrated silica appears at very low levels (~0.1–1%) as a rheology modifier/soft-focus filler or mild absorbent in leave-on skincare (primers, mattifying lotions) and some cleansers. The highest OTC levels are found in abrasive polishing products—especially toothpastes and some exfoliating scrubs—where hydrated silica commonly functions as the primary abrasive at ~20–40% and can reach ~50–60% in high-abrasivity consumer toothpaste/powder formats. It is far less common to exceed low-single-digit percentages in leave-on skincare due to feel/whitening and stability constraints, whereas rinse-off and oral-care formats support much higher loadings.