Deuterium Oxide

This ingredient is also known as heavy water. It is water in which the hydrogen atoms are replaced with deuterium (a stable, non-radioactive isotope of hydrogen).

In cosmetics, it is used as a solvent or formulation component, functionally similar to regular water.

Due to its high molecular similarity to water and low topical reactivity, deuterium oxide does not act as a bioactive skincare ingredient. It does not penetrate the skin in any meaningful way.