Iron oxides may not necessarily sound like an ingredient that you'd find in your skincare or makeup; in our mind, they sound more like something that belongs in a coal mine in West Virginia than on the shelves at Sephora. But iron oxides actually are a very common component in cosmetics.
Ahead, cosmetic chemist Autumn Blum and board-certified dermatologist Kavita Mariwalla, MD, explain more.
Meet the Expert
The primary purpose iron oxides serve is purely functional since they play an integral role in the formulation process. However, there's also a secondary, more skincare-focused benefit that makes them one of those 'get extra bang for your buck' ingredients worth seeking out.
Type of ingredient: Mineral compound
Main benefits: Iron oxides are most often used to add pigment to cosmetics and skincare, but they also have the added benefit of protecting the skin from visible and blue light says Mariwalla.
Who should use it: These are safe and effective for all but can be especially beneficial for those with melasma, a condition that's exacerbated by visible light, explains Mariwalla.
How often can you use it: Daily
Works well with: Iron oxides tend to work well with all ingredients.
Don't use with: According to the experts we spoke with, there are no ingredients known to interact negatively with iron oxides.
What Are Iron Oxides?
Iron oxides are mineral-derived compounds comprised of iron and oxygen. Our coal mine vibes weren't entirely inaccurate; there are several different types of iron oxides, the most commonly known one being rust, says Blum. Obviously, rust isn't what's being put into your skincare and makeup. "Commercially, iron oxides are derived from occurring minerals and pigmented in a lab to control the quality," she explains. "They're often used to add color to cosmetics and skincare." Iron oxides typically come in red, yellow, and black shades, and then have to be blended into the cosmetic or skincare products in order to create the desired color or tint, adds Mariwalla.
Benefits of Iron Oxides
Per our previous point, iron oxides' primary purpose is to give cosmetic products a particular color. But dermatologists are intrigued by this ingredient because iron oxides have also been shown to offer excellent protection against visible light, says Mariwalla. Like UV light, visible light can also be damaging to the skin and, more specifically, it can also worsen conditions such as melasma, Mariwalla adds. In fact, one study found that sunscreen formulas containing iron oxides were more effective at preventing sun-induced pigmentation, especially in darker skin types.
In related news, "iron oxides have been shown to offer enhanced protection against the blue light emitted from our computer screens and electronic devices," says Blum. A study published in The Journal of Cosmetic Dermatology confirmed this, more specifically finding that this benefit was even further enhanced when iron oxides were combined with zinc oxide, an often-used mineral sunscreen ingredient.
Point being, iron oxides offer protection against certain types and wavelengths of light that regular sunscreens do not. And when they're used in sunscreens, they also have the added benefit of adding a nice tint that can make the product more cosmetically elegant and decrease the white cast that many mineral formulas can leave behind, says Mariwalla. Plus, iron oxides also have reflective properties that help to even out skin tone and diffuse the appearance of imperfections, notes Blum. Yes, please.
Side Effects of Iron Oxides
There really aren't any to speak of. "Iron oxides are well-tolerated, even by people with sensitive skin," says Blum. The other upshot? Unlike some of the other pigments used in cosmetics which are animal-derived (carmine is one good example), iron oxides offer a nice vegan alternative for people, she points out.
How to Use
Products with iron oxides can be used daily (and if they're in a sunscreen, they definitely should be used daily). And honestly, it's very likely that they're already found in some of the makeup you're using on the regular. The only thing to keep in mind is that because iron oxides have a larger molecular structure, they can sometimes migrate or fall out of solutions, notes Blum. If you're using a liquid or cream product—like a tinted sunscreen—"it's always a good idea to shake the packaging before using to ensure the color is well-dispersed," she advises.
Dumbuya H, Grimes PE, Lynch S, et al. Impact of iron-oxide containing formulations against visible light-induced skin pigmentation in skin of color individuals. J Drugs Dermatol. 2020;19(7):712-717.
Bernstein EF, Sarkas HW, Boland P. Iron oxides in novel skin care formulations attenuate blue light for enhanced protection against skin damage. J Cosmet Dermatol. 2021;20(2):532-537.