Magnesium oxide is a fine white powder with a dull luster. The substance is comprised solely from one molecule of magnesium and one molecule of oxygen. The compound is commonplace, occurring naturally in the environment. Commercially, magnesium oxide is used in the production of Portland cement, one of the main ingredients in concrete. It is also found in skin care products as both an active ingredient (one that enhances the look and feel of the skin) and an additive (one that improves the quality of a formula). The ingredient is sometimes called magnesia or magnesium alba.
The Scottish chemist Joseph Black first discovered magnesium oxide in 1754. After its discovery, scientists continued to study the substance in hopes of determining what its raw materials were. In 1808, the English chemist Sir Humphry Davy used a mixture of magnesium oxide and a compound formed from mercury and oxygen to finally isolate magnesium from the substance. This marked the discovery of the element magnesium, the eighth most abundant element in the entire universe.
Although magnesium oxide is found naturally in rock and mineral deposits, the substance is typically produced in factories for commercial use. Two methods of manufacturing the ingredient exist. In the first, magnesium carbonate or magnesium hydroxide is put through an intense heat treatment to produce magnesium oxide and byproducts. With the alternate method, magnesium chloride is mixed with lime and then heated.
Magnesium oxide has a pH of 10.3, making it a base on the pH scale. The substance makes an excellent neutralizer for acidic substances. In fact, liquid magnesium oxide is commonly used as a treatment for acid indigestion or heartburn. When added to skin care products, magnesium oxide helps to raise the pH of their formulas. This is beneficial for people with sensitive skin who develop redness and irritation when exposed to harsh, acidic products.
Individual molecules of magnesium oxide are very attracted to water molecules. As a result, the ingredient has the ability to absorb and hold moisture. This property of the compound makes it useful as a desiccant, an additive in powdered skin care products like blushes, eye shadows and facial powder. In such products, magnesium oxide absorbs condensation and helps to keep the formulas more potent, making them apply more evenly and give more appealing results.
Another common use for magnesium oxide is as an opacifying agent in facial cosmetics like foundations and concealers. These products are used to hide imperfections of the skin, so it is important that they are able to fully cover blemishes, discoloration and other flaws. Adding magnesium oxide to the formula of a foundation or concealer makes the product less transparent, allowing it to provide fuller coverage to the complexion. Magnesium oxide is especially useful because it decreases transparency without causing a large increase in the thickness of the foundation. As a result, products that contain the ingredient are highly effective without feeling heavy on the skin.
Historically, magnesium oxide was used in cosmetics and skin care products almost solely as an additive, but the popularity of microdermabrasion has led some skin care companies to use the substance as an active ingredient. Microdermabrasion is a skin treatment in which tiny crystals of diamonds or other gems are used to create friction on the complexion. This friction removes cells from the outer layer of skin and helps to normalize the skin's texture and tone.
In recent years, skin care companies have worked to create topical beauty products that can offer benefits similar to microdermabrasion. Because magnesium oxide is comprised of tiny crystals, it is sometimes added to facial scrubs and moisturizers in an attempt to mimic the gemstone crystals used in microdermabrasion. These products are helpful for performing many of the tasks for which microdermabrasion is commonly used. Among these are lessening the appearance of signs of aging, removing discolored skin tissue and reducing the size of enlarged pores.
The U.S. Food and Drug Administration has listed magnesium oxide as "Generally Regarded as Safe" on its inventory of ingredients used by the beauty industry. The ingredient is not likely to cause side effects when applied to the skin; however, other ingredients in products that contain magnesium oxide could be potential irritants.