Avobenzone vs Benzoic Acid: which is worse?

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.

What is Benzoic Acid?

Benzoic acid is a naturally occurring aromatic carboxylic acid found in cranberries, prunes, cinnamon, and many berries. It is used as a preservative against bacteria, yeast, and fungi at pH below 4.5. In the body, benzoic acid is conjugated with glycine to form hippuric acid, which is excreted in urine.

Documented risks

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.

Benzoic Acid: When benzoic acid (or sodium benzoate) is combined with ascorbic acid (vitamin C) in beverages, it can form benzene, a known carcinogen classified as Group 1 by IARC. This reaction is promoted by heat and light. The FDA and EFSA monitor benzene levels in beverages and have set informal guidance limits. A 1999 Lancet publication and the subsequent 2007 'Southampton study' did not directly involve benzoic acid, but sodium benzoate was included in the tested mixture. Some individuals with aspirin sensitivity may react to benzoic acid. The ADI is 5 mg/kg body weight/day.