Sodium Citrate
Sodium Citrate · INCI Sodium Citrate
Sodium citrate is the sodium salt of citric acid, a plain white salt with no scent or colour. It holds the product at pH 5 to 5.5, close to the skin's own acidity.
It holds the product at the acidity your skin prefers, and keeps it there as the product ages.
What it is
Healthy skin is mildly acidic, sitting at around pH 5. The enzymes that build the barrier's lipids only function properly in acid conditions. The enzymes that break the barrier down speed up as things turn alkaline. The skin's microbes respond to pH too. In laboratory culture, Staphylococcus epidermidis, a helpful resident, grows well at pH 4.7, while Staphylococcus aureus does best nearer neutral. The antimicrobial peptide your own skin makes also works far better in acid than out of it. This is why the pH of anything you leave on your skin matters.
Two things keep each bottle sound. The first is the preservative, a ready-made blend of sodium benzoate and gluconolactone. Sodium benzoate does the preserving, and gluconolactone helps it work. The second is the pH. Sodium citrate buffers the cream at pH 5 to 5.5, close to the skin's own. At the end of making, the pH is checked and fine-tuned with a little sodium hydroxide or citric acid. Sodium citrate holds that pH through the product's shelf life, as things shift and settle.
It has a second job. Trace metals get into every formula, and they catalyse the oxidation that turns oils rancid. Sodium citrate binds them, which helps slow that oxidation. That keeps the oils in good condition, and since oxidised oils can irritate skin, it matters for your skin too.
What it does in our formulas
Sodium citrate holds the product's pH steady and binds the trace metals that speed up oxidation.
It keeps the product at your skin's own acidity
Healthy skin sits at about pH 5, a little acidic. The enzymes that build the barrier's lipids only work in acid conditions, and the enzymes that break the barrier down work faster as things turn alkaline. In laboratory culture, S. epidermidis, one of the skin's helpful residents, grows well in acid conditions, while S. aureus prefers conditions nearer neutral. That is why the pH of a leave-on product matters. Ours sit at pH 5 to 5.5, and sodium citrate is the buffer that holds them there as the product ages.
Well characterisedIt helps slow the oils turning
Trace metals get into any formula, from the water and from the raw materials, and they speed up the oxidation that turns oils rancid. Sodium citrate binds them, which helps slow that oxidation. Oxidised oils can irritate skin, so slower oxidation is better for sensitive skin too.
Well characterisedWhat the research does not show
Sodium citrate is too plain to attract much nonsense, but two claims are worth correcting.
Marketed as A citrus-derived brightening active
Marketed as A chelator that shields your skin from pollution
On the label and in the range
Sodium citrate appears in every one of our formulations, and it sits higher in the list than you might expect for something so anonymous. Holding a pH steady over a shelf life takes a substantial amount. It also holds the pH at which the preservative, sodium benzoate working with gluconolactone, does its job. The exact percentage is published on each product page.
Is it suitable for me?
Sodium citrate has been assessed by the independent expert panel that reviews cosmetic ingredients and found safe as used, and it has a long record as a food additive besides. It suits a vegan routine, sits comfortably on sensitive skin, and carries no restrictions under UK or EU cosmetic law.
As with anything new, if your skin reacts easily it is worth patch testing first.
The research behind this page
We review the published literature. We do not conduct the studies below.
- Proksch E. pH in nature, humans and skin. J Dermatol 2018;45(9):1044-1052. →
- Lambers H, Piessens S, Bloem A, Pronk H, Finkel P. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. Int J Cosmet Sci 2006;28(5):359-370. →
- Fiume MM, Heldreth BA, Bergfeld WF, et al. Safety Assessment of Citric Acid, Inorganic Citrate Salts, and Alkyl Citrate Esters as Used in Cosmetics. Int J Toxicol 2014;33(2 Suppl):16S-46S. →