Sodium Phosphate

Sodium phosphate is primarily a buffering/pH-adjusting and chelating salt typically used at low concentrations in leave-on and rinse-off products, where it is generally well tolerated and not a common cause of irritant contact dermatitis. However, because it can influence product pH and ionic strength (which can sting compromised or eczematous skin, especially near eyes or on fissured areas), it is not truly inert even though reactions are uncommon. In sensitive-skin populations, the realistic risk is low but nonzero, supporting a very gentle score rather than 0.0. Safety Notes: In cosmetics, sodium phosphate (typically mono-/di-/trisodium phosphate used singly or as part of phosphate buffer systems) is most often present at low levels (~0.05–0.5%) in leave-on lotions/serums and rinse-off cleansers to adjust and stabilize pH, chelate/assist stability, and support preservative performance. Higher-strength consumer products—especially exfoliating/clarifying masks, bath/cleansing powders, and some hair-color/bleach-related or high-alkalinity cleansing systems available retail—can use phosphate salts at ~1–3% to deliver stronger buffering/alkalinity control and formulation robustness; above this is uncommon in mainstream OTC skincare due to sensorial and pH/irritation constraints.