Mineral pH buffer. Together with sodium dihydrogen phosphate it keeps formula pH near the physiological 5.5-6.5. No sensorial impact and no skincare effect. Pregnancy-safe.
Topical application
BLimited evidence. One RCT or several controlled studies with limitations.
Functional pH buffer with a long history of use in cosmetics, pharmacology, and food. Safety confirmed by EFSA and FDA. No standalone activity.
Disodium Phosphate (Na2HPO4) is an inorganic sodium salt of orthophosphoric acid. In pharmaceutical and cosmetic formulas it works as a pH buffer: paired with sodium dihydrogen phosphate (NaH2PO4) it forms a phosphate buffer system stable in the pH range 6.0-7.5. INCI: Disodium Phosphate. Food code E339(ii). In cosmetics it is used at 0.05-0.5% to keep the formula at its target pH. Particularly important in toners, essences, vitamin C serums (low pH 3.5 required), AHA/BHA exfoliants (pH 3.5-4.5), and niacinamide creams (pH 5.5-7). Without a buffer, pH drifts over time and actives lose efficacy or start to irritate. Pregnancy safety. Topical use is safe. Systemic absorption through the skin is minimal. Disodium phosphate is also used in injectable pharmacology – the human safety profile is established. Skin tolerance. Low irritation and allergen potential at cosmetic concentrations. At very high levels (>5%) it can slightly irritate mucous membranes – these levels are not used in cosmetics. No standalone active effects. This is a background ingredient that keeps other ingredients working. Marketing rarely calls it out, but without a buffer most active formulas do not perform as claimed.
Irritation potential
LowAllergen risk
LowPregnancy
SafeSuitable for
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Disodium Phosphate is considered safe during pregnancy at typical cosmetic concentrations. Systemic absorption through the skin is minimal.
Disodium Phosphate suits: normal, dry, combination, oily, sensitive.
Mineral pH buffer.
On the Fulton scale 0/5 – non-comedogenic. For acne-prone skin, a rating of 3 or higher suggests choosing an alternative.
The INCI name is Disodium Phosphate. It may also appear as: Sodium Phosphate Dibasic, Na2HPO4, Динатрия фосфат.
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