Avobenzone vs Calcium Propionate: 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 Calcium Propionate?

Calcium propionate is the calcium salt of propionic acid, a short-chain fatty acid naturally produced during fermentation. It is one of the most widely used mold inhibitors in commercial bread and baked goods. It works by penetrating fungal cells and lowering internal pH to inhibit growth.

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.

Calcium Propionate: Generally recognized as safe. However, a 2012 study in the Journal of Pediatric Child Health (Dengate & Ruben) and a 2019 study published in Science Translational Medicine found that calcium propionate induced insulin resistance in a mouse model and raised metabolic concerns. The 2019 animal study, conducted by Bhatt et al., found that propionate triggered glucagon and norepinephrine secretion. Some open-label human studies and parental reports have linked calcium propionate to irritability, sleep disturbance, and behavioral changes in sensitive children, though these lack robust clinical trial evidence. Most regulatory agencies consider it safe at current use levels.