Messi Biology states that among the dazzling array of ingredients on cosmetic labels, “magnesium hydroxide” might be an unfamiliar name. However, this seemingly ordinary inorganic compound has long since become a key auxiliary ingredient for enhancing product performance. As a safe raw material complying with the Safety and Technical Standards for Cosmetics, it plays an essential role in skincare, color cosmetics, and other fields due to its weak alkalinity, low irritation, and multifunctionality.
The core advantages of cosmetic-grade magnesium hydroxide stem from its unique physical and chemical properties. As a weak inorganic base, it only slightly ionizes in water, and its decomposition products are magnesium oxide and water, leaving no toxic residues and making it friendly to both the human body and the environment. Its powder form provides good adsorption capabilities, while its mild alkalinity makes it a natural pH regulator. These characteristics allow it to adapt to various cosmetic requirements. Notably, its addition level in cosmetics is typically ≤1%, and the heavy metal content of high-purity raw materials must be controlled below 10 ppm to ensure safety in use.
In skincare products, magnesium hydroxide acts as a “regulator” to balance formulations. In facial cleansers, it neutralizes fatty acids and adjusts the pH to 6.5–8.0, maintaining cleansing power while avoiding excessive irritation to the skin barrier. In exfoliating products containing alpha hydroxy acids (AHAs) or salicylic acid, it serves as a buffer to stabilize the pH, reducing irritation reactions such as redness and peeling. Oil-control masks and clay masks utilize its adsorption properties, combining it with ingredients like kaolin clay to absorb excess sebum on the skin surface and improve the appearance of enlarged pores, making it particularly suitable for oily skin.
In the field of color cosmetics, magnesium hydroxide is a “secret weapon” for improving skin feel. Adding 3–10 wt% of magnesium hydroxide to loose and pressed powders can enhance both the smoothness and adhesion of the powder, while absorbing sweat and sebum to prevent makeup from creasing or becoming patchy, thereby extending makeup wear. In foundations and concealers, it adjusts the pH to help the powder adhere better to the skin while assisting in sebum absorption, giving a more natural matte finish. Its white powder characteristics also provide a slight light-scattering effect, adding a natural brightening look to the skin.
In special functional cosmetics, the synergistic effects of magnesium hydroxide are particularly prominent. In anti-acne products, it neutralizes the acidity of ingredients like sulfur, reducing irritation while absorbing inflammatory secretions to help alleviate acne issues. In physical sunscreens, it regulates the formulation pH to prevent the agglomeration of UV filters such as zinc oxide and titanium dioxide, ensuring an even and stable sun protection effect. Some antibacterial products utilize its weak alkalinity to inhibit the growth of Cutibacterium acnes (formerly Propionibacterium acnes), reducing skin inflammatory responses.
When using cosmetics containing magnesium hydroxide, individuals with sensitive skin should pay extra attention. Although its irritation potential is low, high-concentration products may disrupt the skin’s natural acidic barrier (healthy skin has a pH of approximately 5.5). It is recommended that those with sensitive skin choose low-concentration or additive-free formulations. Consumers can check the ingredient list for the raw material under its INCI name “Magnesium Hydroxide” to make rational product choices. This ingredient, derived from natural minerals or extracted from seawater, has become an all-rounder in the cosmetics industry due to its mild and safe properties. From balancing pH levels to absorbing sebum, and from stabilizing formulations to soothing inflammation, magnesium hydroxide protects skin health in a low-profile manner, making it an indispensable invisible helper in cosmetics.