What is Sodium Benzoate?
Sodium benzoate is a salt made of sodium and benzoic acid. It can be found naturally in fruit and spices like apples, cranberries and cinnamon. Despite being naturally occurring, it is usually synthesised in a lab when needed in large quantities for cosmetics. It is also used as a preservative in food and drink.
Sodium benzoate is a popular ingredient in cosmetics, not because of some amazing skin care property but because it works as a preservative. When an active ingredient in a skin care product like a nutrient or vitamin is used to nourish your skin cells, chances are the same nutrients also make good food for microbes in the air which can colonise your product and turn it mouldy. By including sodium benzoate alongside the active ingredient, you can extend the life span of the product and fight off the growth of mould.
How does it work?
Just like animals and plants, the yeast cell that make up mould need sugar to survive. In yeast, the sugar gets processed by the cells to give energy, carbon dioxide and ethanol, the same process used in wine and beer making. Benzoic acid gets taken up into the yeast cells where it messes with the acidity and stops them turning sugar into alcohol. As they can’t make energy, they die and won’t form a mould colony on the product.
It’s possible to be allergic to benzoic acid and if so it can cause severe swelling, itching and difficulty breathing.
It may cause a burning sensation even in those who are not allergic to it.
Benzoic acid can form trace amounts of benzene under certain conditions like UV light exposure, heat and combination with vitamin C. Benzene is a known carcinogen but as benzoic acid should not be in concentrations above 0.5% and only a fraction of this may for benzene, the amount formed is unlikely to be hazardous. Benzoic acid is not thought to accumulate in the body so regular small, safe doses shouldn’t add up into one large, hazardous dose.
Sodium benzoate may interact with corticosteroids, haloperidol, sodium valproate and valoproic acid.
Sobenate, antimol, benzoic acid sodium salt, benzoate of soda, natrium benzoicum, carboxybenzene sodium salt
- Krebs, H.A., et al., Studies on the mechanism of the antifungal action of benzoate. Biochemical Journal, 1983. 214(3): p. 657-663.