Silica
Also known as Amorphous silica, Synthetic amorphous silica, SAS, Silicon dioxide (amorphous), Fumed silica, Precipitated silica
“CIR Expert Panel says: safe as used in cosmetics.”
Cosmetic silica is amorphous (synthetic amorphous silica, SAS; CAS 7631-86-9), which is chemically and toxicologically distinct from crystalline silica (CAS 14808-60-7, an IARC Group 1 inhalation carcinogen not used in cosmetics). CIR assessed amorphous silica and found it safe (Final Report 09/09). Skin penetration studies confirm SAS does not penetrate intact skin at relevant cosmetic use concentrations. A 2025 CIR amended assessment reaffirmed safety in the present practices of use when formulated to be non-irritating. Review literature finds no novel toxicological mechanism for SAS. Concerns about inhalation toxicity for crystalline silica are not applicable to the cosmetic-grade amorphous form.
Absorbent and anti-caking agent that controls excess oil/sebum in skin and hair products
Bulking and opacifying agent used in powders, foundations, and sunscreens
Improves slip, spreadability, and sensory feel in leave-on formulations
Chemically inert and non-reactive with other formulation components
CIR Expert Panel concluded safe as used in cosmetics (Final Report 09/09)
- · Crystalline silica (CAS 14808-60-7, quartz/cristobalite) is an IARC Group 1 inhalation carcinogen — this is NOT the cosmetic grade. Cosmetic silica is always amorphous.
- · Nanoparticle amorphous silica has been examined for cytotoxic and inflammatory potential in vitro; dermal route studies confirm no significant skin penetration at cosmetic use levels.
Powder/aerosol formulations using amorphous silica carry theoretical inhalation risk; CIR sister ingredients Silica Dimethyl Silylate and Silica Silylate carry a respiratory-tract condition (SQ) for this reason. The plain amorphous silica CIR finding is S with no condition, but formulators should avoid inhalable aerosol formats.
CIR Quick Reference Table (12/2017, revised 07/2018) — Silica (amorphous) row: Finding=S, Citation=Final Report 09/09 available from CIR
“Silica (amorphous) | S | | Final Report 09/09 available from CIR”— QRT-122017revised072018.pdf, p. 117