Magnesium oxide (MgO) is an inorganic compound that is widely used in cosmetic formulations as a fine, white powder. In creams, powders or lotions, it serves as a white colorant (CI 77711), which gives the formulation opacity or optical brightness. It also helps to absorb excess sebum and thus ensures a matte complexion. At the same time, its buffering effect can stabilize the pH value of the product and contribute to the desired opacity and consistency. Due to its properties, magnesium oxide is a common excipient in decorative cosmetics and sun protection products(1).