Ascorbic Acid vs Avobenzone: which is worse?

What is Ascorbic Acid?

Ascorbic acid is the chemical name for vitamin C, an essential water-soluble vitamin found abundantly in fruits and vegetables. As a food additive (E300), it functions as an antioxidant preservative, preventing oxidative browning and rancidity. Commercial ascorbic acid is produced by fermentation of glucose, most commonly from corn.

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

Ascorbic Acid: Generally recognized as safe. Note: when ascorbic acid is combined with sodium benzoate or benzoic acid in acidic beverages, benzene can form — a Class 1 carcinogen. This combination should be avoided in formulations. As a standalone additive, ascorbic acid is not only safe but nutritionally beneficial. Very high supplemental doses (>2 g/day) can cause diarrhea and kidney stone risk in predisposed individuals.

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.