Sodium benzoate is the sodium salt of benzoic acid and has been used as a preservative in various industries, including cosmetics, for over a century. Its effectiveness as an antimicrobial agent is primarily due to its ability to penetrate cell membranes and disrupt cellular functions in microorganisms when in its undissociated form [1].

In skincare formulations, sodium benzoate is particularly effective in acidic environments (pH below 4.5), where it exists predominantly in its undissociated form. This property makes it an excellent preservative for many water-based cosmetic products. However, its efficacy decreases in products with higher pH levels [2].

While sodium benzoate is generally recognized as safe (GRAS) by the FDA for use in foods and cosmetics, some concerns have been raised about its potential to form benzene, a known carcinogen, when combined with ascorbic acid (vitamin C) under certain conditions. However, this reaction is unlikely to occur in properly formulated cosmetic products [3]. Additionally, some individuals may experience skin irritation or allergic reactions to sodium benzoate, although such occurrences are relatively rare [4].