What it is
Sodium metaphosphate is a condensed sodium phosphate that binds metal ions and helps control the ionic environment of a formula. By sequestering trace metals it can support product stability and the performance of preservatives and other ingredients. In sunscreens it is typically present at low levels as a stabilizing and pH-related aid rather than as an active ingredient.
Safety & warnings
At the low levels used in cosmetics, inorganic phosphate salts of this kind are generally well tolerated and are not fragrance allergens. They are water-soluble and not considered comedogenic.
Origin & sourcing
Synthetic; an inorganic salt produced from sodium and phosphate sources.
Questions everyone asks
Why is sodium metaphosphate added to sunscreen?
It acts as a chelating and buffering aid that binds trace metal ions and helps keep the formula stable.
Is it an active sun-protection ingredient?
No. It is a low-level stabilizing aid and does not provide UV protection.