Zinc oxide is a compound formed from a combination of one molecule of the mineral zinc and one molecule of oxygen. Zinc is one of the most abundant elements on the Earth and is a silver-colored metal with a medium luster. When the metal combines with oxygen, it forms a white powder that slightly resembles flour or baking soda.
For use in skin care and cosmetics products, zinc oxide can be produced through several methods. One way, called the French or direct process, involves heating pure zinc metal at extremely high temperatures until it forms a vapor and mixes with the air. Then, the air is cooled, and the zinc oxide is captured in a special bag. This produces a potent, high quality form of the ingredient.
The same method can be used with zinc that has already combined with other elements. Known as the indirect or American process, this technique results in a finished product that is of lower potency.
In laboratory settings, zinc oxide can be produced by combining different chemicals with solutions that contain zinc. Another way to synthesize the ingredient is to pass electricity through a zinc electrode that is submerged in a liquid that contains oxygen in its molecules. These methods are used to produce large batches of medium-quality zinc oxide.
The use of zinc oxide in natural medicine dates back as far as 500 BC, when it was used as an ointment in Ancient India. By 1025, European physicians, including the Greek doctor Dioscorides, were using zinc oxide to treat growths on the skin, such as cancerous lesions. As research continued, the uses of zinc oxide expanded, and in the 20th century, mass-produced skin care products that contain the ingredient first appeared on the market.
During the 1970s, the U.S. Food and Drug Administration began regulating the production of sunscreens, products that are used to protect the skin from ultraviolet rays. Zinc oxide is one of 17 approved substances that can be used as a sun-protective ingredient in sunscreens. Of these ingredients, zinc oxide is known to absorb the most ultraviolet energy and protects against both UVA and UVB rays, the two forms of sun energy that are the most damaging for the skin.
Zinc oxide sunscreens help to prevent the redness and irritation known as sunburn that happens as a result of prolonged exposure to the sun. These sunscreens also help limit the amount of cellular damage that occurs when the skin is subjected to ultraviolet energy. By reducing the amount of damage, zinc oxide sunscreens help to prevent sun damage that can lead to signs of premature aging. In addition, using a zinc oxide sunscreen greatly reduces the risk of developing melanoma and other forms of skin cancer that are typically caused by the sun.
The FDA lists zinc oxide in its "Generally Regarded as Safe" ingredient category. The chemical is non-toxic and rarely causes side effects when used as a sunscreen. In addition, zinc oxide does not penetrate the pores, so it does not lead to acne breakouts or enlarged pores. One drawback to zinc oxide is that formulas that contain it are a bright white color, which some people feel detracts from their appearance. Sunscreens that contain nano-molecules often appear less white in color, as their smaller size allows them to reflect less light in one area, making them less noticeable. Some brands tint their products so that they do not create a white cast on the skin.
In addition to its use in sunscreens, zinc oxide has other applications in skin care products. The powder is often used as a thickening agent to make creams and lotions more luxurious in texture. The thick nature of zinc oxide also makes it effective as a skin protectant. Many diaper creams and formulas designed to prevent chaffing include zinc oxide. These products cut down on the amount of friction that occurs when fabric or skin rubs against skin tissue.