Iron oxides are a group of compounds made up of iron and oxygen linked together by chemical bonds. The rust you see on metal is an example of natural iron oxide formation. Rust forms when iron is exposed to oxygen and water, and a chemical reaction called oxidations occurs. During the rusting process, iron atoms bond with oxygen atoms to create iron oxides that are typically red, brown or orange in color. Water is necessary for iron oxides to form, either in the form of water or moisture from the air. Most iron oxides are now produced synthetically under more controlled circumstances since naturally oxidized iron can contain impurities like heavy metals that aren't desirable and may be harmful.
Iron oxides abound in nature where they serve a variety of biological functions. In addition, they're used as an ingredient in household and personal care products. One way they're commonly used is to make paint pigments used by artists. They're also used to dye concrete, tiles, rubber and leather. Iron oxides form deep yellow or orange shades and various shades of red and brown, so they're ideal for creating earth-tone paints and pigments. There are also black oxides that are deep black in color. Iron oxides have been used as paint pigments since very early times to create earthy colors like umber and sienna that artistic people can use to paint realistic landscape paintings.
Iron oxide is also used in the manufacture of electronic parts and magnets and to create the magnetic strip on the back of credit cards and ATM cards. In addition, they're used in the pharmaceutical industry to add color to tablets and capsules. More recently, iron oxide nanoparticles have been used to deliver drugs and medications to specific areas of the body.
Another area were iron oxides are useful is in the cosmetic and personal care industry, Because iron oxides come in shades or red, orange, brown and black, cosmetic manufacturers use them to add color to cosmetic products like eye shadow, blush, face powders, lipstick and mineral makeup. Using iron oxides as coloring agents in cosmetics has some advantages. They're resistant to moisture, don't easily bleed or smear and have "staying power" so you don't have to keep reapplying your eye shadow or blush. They also create intense pigments that have a rich color.
Iron oxide pigments work well in makeup products that remain on the surface of the skin, but they aren't ideal for permanent makeup placed beneath the skin. When they're placed into the dermis of the skin during the application of permanent makeup, the iron is gradually absorbed by blood vessels in the dermis, and the color can change or fade. Therefore, iron oxide pigments aren't truly permanent when injected subcutaneously.
Iron oxides are found in a wide array of cosmetic products from eye shadow to talcum powder - even products that are marketed as natural or organic. That's because they're safe, although the iron oxide in cosmetics is made synthetically. Iron oxides are made in a lab for safety reasons since naturally produced varieties often contain impurities. These impurities aren't an issue when iron oxides are made under carefully controlled conditions. Cosmetic-grade iron oxides are made from mined iron salts that are then oxidized in a laboratory and purified. Oxides formed in a natural, uncontrolled setting are often contaminated with heavy metals like arsenic, mercury and cadmium. This is an example of natural not always being safer.
Iron oxides are gentle and non-toxic in cosmetic products placed on the surface of the skin, although they aren't suitable for permanent cosmetics placed into the dermal layer of the skin since they can be absorbed by blood vessels and lead to color changes. They're usually not irritating to the skin and aren't known to allergenic. The few reports of allergic reactions to iron oxides have turned out to be an allergy to nickel instead. Iron oxides typically don't cause problems even for people with sensitive skin. All in all, they're safe and non-irritating in the amounts found in cosmetic products.