Sodium Hexametaphosphate

Sodium hexametaphosphate is a chelating/sequestering agent used at low levels (typically well under 1%) to bind metal ions and improve product stability and performance. Human irritation risk at these cosmetic concentrations is generally low, but as an inorganic phosphate salt it can contribute to stinging or irritation on compromised skin (e.g., eczema flares) and is not as universally inert as water or simple emollients. Given sensitive-skin and barrier-impaired populations, I rate it as gentle but not irritation-free. Safety Notes: Sodium hexametaphosphate is used in skincare/personal-care primarily as a chelating/sequestering agent and water-softener aid, and in real-world leave-on products it is typically present at very low levels (often ~0.01–0.3%) to improve stability and reduce metal-ion catalyzed discoloration/odor. In rinse-off cleansers, shampoos, and bath products it is also used for water-softening/anti-soap scum and can be found at higher levels, with some OTC consumer formulations (including hard-water/clarifying or chelating-focused products and some exfoliating/scrub-type systems) reaching into the low single digits; around 5% represents the upper end observed for consumer-available rinse-off products, with higher levels being uncommon due to sensorial, pH/ionic strength, and deposition/stability constraints.