Etidronic acid is used as a chelating agent in cosmetics. It forms complexes with calcium, arsenic, iron and other metal ions to neutralize them. This allows you to manage the use of slightly "hard" water, which could, for example, affect the surfactants of the product. Chelators are often used in softeners. This molecule is safe for human health, but has the disadvantage is that, like EDTA, it is very poorly biodegradable and the complexes it forms with metals are scattered in nature.