Tetrasodium Etidronate

Tetrasodium etidronate is a chelating agent used at very low concentrations (typically well under 1%) to improve formula stability by binding metal ions. In routine cosmetic use it is generally well-tolerated, but as a multi-charged chelator it can cause occasional stinging or irritation in highly compromised skin or around the eyes, so it is not considered completely inert. Overall, clinical and patch-test experience supports a very gentle risk profile when used at standard leave-on and rinse-off levels. Safety Notes: Tetrasodium etidronate is used primarily as a chelating/sequestrant to improve stability (especially in the presence of metal ions) and boost preservative performance; in mainstream leave-on skincare and color cosmetics it is commonly seen around 0.01–0.1%, with the lowest commercial uses observed near ~0.005% where it is a minor supporting stabilizer. Higher consumer-available levels are found in some rinse-off cleansing products, soaps, and hard-water/soap-scum control formulations where chelation demand is greater, with market-available high-strength products reaching about 0.2–0.3% while remaining within typical safety expectations for cosmetic rinse-off use.