Sodium Benzoate
Also known as Benzoic acid sodium salt, Sodium benzoate, E211, Benzoate of soda
“CIR Expert Panel says: safe as used in cosmetics.”
Sodium Benzoate (sodium salt of benzoic acid; CAS 532-32-1; C7H5NaO2) is a commonly used preservative in cosmetic, food, and pharmaceutical formulations. It functions via pH-dependent antimicrobial activity: at low pH (below ~5.5) the equilibrium shifts toward the free benzoic acid form, which is the active antimicrobial species. Accordingly, sodium benzoate is most effective in low-pH formulations and is commonly paired with pH-lowering ingredients like citric acid to ensure antimicrobial activity. It is often combined with potassium sorbate in a 'natural preservative system' common in clean-beauty and food-adjacent cosmetic formulations. The Cosmetic Ingredient Review Expert Panel originally assessed Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate together in 2001 (Int J Toxicol 20(Suppl 3):23-50, PMID 11766131) with a conclusion of safe up to 5%. In 2017, the Panel re-reviewed these ingredients as part of an amended assessment that also covered additional benzoic acid salts and benzyl benzoate (Johnson, Bergfeld, Belsito et al., Safety Assessment of Benzyl Alcohol, Benzoic Acid and its Salts, and Benzyl Benzoate, Int J Toxicol 36(Suppl 3):5S-30S, 2017, PMID 29243541). The 2017 re-review concluded these ingredients are safe as used in cosmetics — the QRT row reflects the 2017 finding as 'S' (plain Safe) without the 2001 concentration qualifier, meaning the updated assessment did not carry forward the 5% cap. Sodium Benzoate is FDA GRAS as a direct food additive and widely used as food preservative E211. WHO established an acceptable daily intake of 5 mg/kg for the benzoic acid / sodium benzoate / benzyl alcohol group. The QRT row carries no conditions or concentration limits for current cosmetic use.
Broad-spectrum antimicrobial at low pH — effective against bacteria, yeasts, and molds in acidic cosmetic formulations
FDA Generally Recognized As Safe (GRAS) as a direct food additive (E211); long history of safe food and cosmetic use
CIR Expert Panel concluded safe as used in cosmetics (Johnson et al. IJT 2017, PMID 29243541; original 2001 assessment PMID 11766131) — without concentration restriction in the updated assessment
Commonly paired with potassium sorbate in 'natural preservative system' formulations common in clean-beauty and food-adjacent cosmetics — the pair gives broader antimicrobial coverage than either alone
WHO acceptable daily intake of 5 mg/kg body weight for the benzoic acid / sodium benzoate group supports the long history of safe dietary exposure
- · The 2001 original CIR assessment had a 5% concentration cap; the 2017 amended re-review concluded safe without that cap, which the QRT 'S' finding reflects
pH-dependent activity — sodium benzoate is only antimicrobially effective at low pH (below about 5.5); at higher pH the benzoate ion predominates and is largely inactive, so it cannot be used as a standalone preservative in neutral or alkaline formulations
In the presence of ascorbic acid (vitamin C) and UV light, sodium benzoate can form trace amounts of benzene via decarboxylation — a concern primarily in acidic beverages rather than typical cosmetic formulations, but formulators should be aware when combining sodium benzoate with vitamin C serums exposed to light
CIR Quick Reference Table (12/2017, revised 07/2018) - Sodium Benzoate row: Finding 'S' (Safe), Citation 'IJT 36(Suppl. 3):5-30, 2017; IJ…
“Sodium Benzoate | S | [no detail column entry] | IJT 36(Suppl. 3):5-30, 2017; IJT 20(S3):23-50, 2001”— QRT-122017revised072018.pdf, p. 118