Messi Biology states that the underarm is naturally odorless; the true source of odor is actually bacteria. When proteins in sweat are broken down by microorganisms in the armpits into unsaturated fatty acids, unpleasant odors follow. Deodorant sticks on the market generally follow two main approaches: using aluminum salts to “block” sweat glands and reduce perspiration, or “redirecting” bacterial proliferation at the source. In this “redirection” approach, a white, fluffy powder plays a crucial role—basic magnesium carbonate.
Basic magnesium carbonate is not pure magnesium carbonate, but a double salt formed by the combination of magnesium carbonate and magnesium hydroxide in a specific proportion. Under an electron microscope, it exhibits a “rosette” structure composed of countless fine needle-like crystals filled with internal micropores, resulting in a specific surface area far exceeding that of ordinary heavy carbonates. It is as light as down, boasts an oil-absorption capacity three times that of calcium carbonate, and is non-toxic, odorless, and highly white. These properties led British cosmetic manufacturers to widely apply it in deodorants and makeup products more than 60 years ago.
1. Moisture Absorption and Dryness Champion: Deodorant sticks are typically structured around wax bases and polyols, while the porous crystals of basic magnesium carbonate act like countless miniature “adsorption sponges,” rapidly capturing sweat and sebum on the skin’s surface to reduce underarm dampness and stickiness. An addition level generally controlled between 1% and 5% achieves long-lasting dryness.
2. Acid-Base Neutralization and Odor Removal: Sweat and bacterial metabolites tend to be acidic, whereas basic magnesium carbonate has a mild, weakly alkaline pH of about 8–9. It slowly neutralizes acidic substances on the skin’s surface, which not only inhibits the environment for bacterial proliferation but also directly adsorbs odor molecules, alleviating body odor at the source.
3. Fragrance Fixative: Its large specific surface area grants it exceptional carrier capabilities—it can both adsorb fragrance molecules and release them slowly, making the top, middle, and base notes of a deodorant stick last longer and preventing the scent from fading too quickly.
4. Formula Stabilization Assistant: Basic magnesium carbonate can act as a “glidant” for powders like talc, preventing the powder from “pilling” or clumping. At the same time, its fine particles improve the spreadability and application of the stick paste, allowing it to glide smoothly across the armpits without leaving white residue.
Traditional antiperspirants rely on aluminum salts that form gels upon contact with sweat to temporarily block sweat glands. While their sweat-control capability is strong, some sensitive skin users may experience stinging, dryness, or follicular discomfort. In contrast, magnesium-based solutions represented by basic magnesium carbonate follow a route of “physical adsorption and mild neutralization.” They do not disrupt normal perspiration and feature excellent biocompatibility, making them friendlier for sensitive and eczema-prone skin, and increasingly popular in natural deodorant formulas.
In engineering practice, basic magnesium carbonate is typically combined with magnesium hydroxide to form a “magnesium-containing composition,” where the former focuses on adsorption and fragrance retention, and the latter strengthens antibacterial and odor-removing effects. From a twist-up deodorant stick to baby powder, basic magnesium carbonate relies on its porous structure and mild alkalinity to support the dry framework of deodorant products. Understanding its mechanism of action is understanding the scientific code behind staying “fresh all day long.”