Silicon Dioxide vs Avobenzone: which is worse?

What is Silicon Dioxide?

Silicon dioxide (silica) is a naturally occurring mineral compound used as an anti-caking agent in powdered and granular foods. The food-grade form is amorphous (non-crystalline) synthetic silica, distinct from the crystalline quartz form associated with lung disease. It absorbs moisture and prevents clumping in powders.

What is Avobenzone?

Avobenzone (INCI: Butyl Methoxydibenzoylmethane) is a chemical UV filter that is the only FDA-approved broad-spectrum UVA-absorbing active sunscreen ingredient in the US that covers the full UVA spectrum (320–400 nm). It is inherently photounstable and must be combined with photostabilizers.

Documented risks

Silicon Dioxide: Food-grade amorphous silicon dioxide is generally recognized as safe. EFSA re-evaluated it in 2018 and concluded there was no safety concern at typical dietary exposure levels; however, the panel noted uncertainty about nanoparticle forms. The food form should not be confused with crystalline silica (quartz) dust, which is a recognized carcinogen when inhaled occupationally. Ingested amorphous silica passes through the body largely unabsorbed.

Avobenzone: Avobenzone is effective and considered safe at approved concentrations (up to 3% in US OTC sunscreens). A 2019 FDA study found that several sunscreen actives including avobenzone were systemically absorbed above the 0.5 ng/mL threshold after repeated use, triggering a call for additional safety data. This does not indicate harm, but the FDA requested more studies under its proposed sunscreen monograph. Current evidence supports its continued safe use. No clear endocrine disruption or carcinogenicity at human exposure levels is established.