Potassium Benzoate

Potassium benzoate is a benzoate preservative typically used around ~0.1–0.5% and is generally well tolerated, but it can sting on compromised skin because benzoates can convert to benzoic acid depending on formula pH and skin conditions. Clinical and consumer patch testing suggests low overall irritancy, yet eczema-prone or barrier-impaired patients can experience burning or dermatitis more often than with truly inert humectants/emollients. Given preservative-related sensitivity risk in reactive populations, I rate it as mild rather than gentle. Safety Notes: In consumer skincare, potassium benzoate is used primarily as a preservative (benzoate system) and is most often seen around ~0.1–0.5%, with low-end usage (~0.05%) appearing in multi-hurdle formulas (e.g., combined with potassium sorbate/phenoxyethanol, chelators, low pH) in both rinse-off and leave-on products. High-end consumer-available products (especially “natural/ECO” or organic-leaning leave-on lotions/serums and some rinse-off cleansers relying on benzoate/sorbate systems) can reach ~1.0% total potassium benzoate to meet preservation needs at acidic pH, staying within common regulatory expectations for benzoic acid/benzoate use in cosmetics.