Benzoic Acid

Benzoic acid is a simple aromatic carboxylic acid that occurs naturally in many plants and fruits, including cranberries, prunes, and cinnamon, and has been used as a food and cosmetic preservative for over a century. Its antimicrobial efficacy is highly pH-dependent — it works primarily in its undissociated form, making it most effective in acidic formulations below pH 5.0, where it disrupts microbial cell membrane function and inhibits enzymatic activity. Formulators favor it for its long safety track record, low cost, and synergistic activity with other preservatives such as sodium benzoate and phenoxyethanol, though its use is regulated (typically up to 0.5% in rinse-off and leave-on products in the EU) due to potential sensitization concerns.