Namely
Etidronic acid is used as a chelating agent in cosmetics. It creates complexes with calcium, arsenic, iron and other metal ions to neutralize them. This makes it possible to manage the use of slightly "hard" waters, which could interfere with the surfactants of the product for example. Chelators are often used in water softeners. This molecule does not pose any problems for human health, its disadvantage is that, like EDTA, it is very little biodegradable, and the complexes it forms with metals are found scattered in nature.