Skincare Ingredients: Sodium Benzoate

What is Sodium Benzoate?

INCI: Sodium Benzoate

Great for: Preservation against fungus and yeast. It shows some activity against bacteria.

How it works: Sodium Benzoate is a food grade preservative regarded as safe worldwide. It is generally used at concentrations of .1 to .2 percent.  As benzoic acid, it is considered to be primarily an anti-fungal, but it shows some activity against bacteria. Since it is not a broad spectrum preservative for cosmetic use, it should be combined with other preservatives that help protect against bacteria. Benzoic acid, the product of sodium benzoate and water, becomes inactive by non-ionics and too high a pH.

Where does Sodium Benzoate come from?

Sodium benzoate occurs naturally, along with benzoic acid and its esters in foods such as cranberry, bilberry, prawns, milk, cheese, and yogurt.  It is the inactive salt of benzoic acid and can be produced by reacting sodium hydroxide with benzoic acid. Sodium benzoate is soluble in water where it converts to benzoic acid, its active form, at a low pH.

Formulation notes

Sodium benzoate is often combined with potassium sorbate in low pH products to provide a synergistic preservative effect against yeast and mold. Benzoic acid is very pH dependent. While it shows some activity up to pH 6 (about 1.55%), it is most active at pH 3 (94%). If it is used as a preservative, the pH of the finished product may need to be lowered. According to Lotion Crafters, the use of sodium benzoate and L-Ascorbic acid and citric acid in the same cosmetic formulations should be avoided.


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