What Are Iron Oxides?
Iron oxides are skincare and cosmetic ingredients that are used to color formulations. Iron oxides are used in three basic shades: black (CI 77499), yellow (CI 77492) and red (CI 77491).
Iron oxides are made up of iron and oxygen and have been used as coloring agents in cosmetics since the early 1900s. Iron oxides occur naturally, for example, rust is a type of iron oxide. Red iron oxide can be naturally derived from the mineral hematite; yellow iron oxides come from limonites such as ochers, siennas, and umbers; black iron oxide is obtained from the mineral magnetite. However, the iron oxides used in cosmetics are usually synthetic. There are a total of 16 different iron oxides used in cosmetics. In addition, to use in cosmetics, iron oxides can be found in paints, coatings, and colored concretes.
Iron oxides are closely regulated by the US Food and Drug Administration. The US Food and Drug Administration’s Code of Federal Regulations for iron oxides states, ‘Synthetic iron oxides are produced in various ways, including thermal decomposition of iron salts, such as ferrous sulfate, to produce reds; precipitation to produce yellows, reds, browns, and blacks; and reduction of organic compounds by iron to produce yellows and blacks.’
the good:Iron oxides are used to improve the color of cosmetics and skincare products to improve how they look.
the not so good:Iron oxides are not used to improve the condition of the skin and are only used to increase the view appeal of the formulations.
Who is it for?All skin types except those that have an identified allergy to it.
Synergetic ingredients:Works well with most ingredients.
Keep an eye on:There is a difference between the level of impurities between the natural and synthetic forms of iron oxides. Synthetic iron oxides are generally considered to be safer than natural forms.
Why Are Iron Oxides Used?
In cosmetics and skincare products, iron oxides function as colorants. They are the main pigments used for matching skin tones in foundations, powders, concealers, and other make up for the face. Iron oxides can also be found in eye shadows, blushes, powders, lipstick, and mineral makeup. Iron oxides are available in three basic shades: black (CI 77499), yellow (CI 77492) and red (CI 77491). There are also various shades of brown iron oxides, but these are just mixtures of the three previously mentioned colors.
Iron oxides are opaque and have excellent light stability, however, yellow and black iron oxides are sensitive to high temperatures. Iron oxides are also resistant to moisture, so they won’t easily bleed or smear. Iron oxides have excellent ‘staying power’, which means that the product will last for a long time without needing to be reapplied.
Natural vs. Synthetic: Which Is Better?
Iron oxides are considered to be safe as used in cosmetics and personal care products because they are non-toxic and non-allergenic. Iron oxides are even well tolerated by those with sensitive skin. Even though iron oxides are synthetic ingredients, they are still often used in products that are marketed as natural or organic. This is because the synthetic versions of iron oxides are actually safer than the natural versions, which often contain impurities. For instance, oxides formed in a natural, uncontrolled setting are often contaminated with heavy metals. This demonstrates that just because an ingredient is natural does not always mean it is safe.
Are Iron Oxides Safe?
The Cosmetic Ingredient Review (CIR) Expert Panel, a group responsible for evaluating the safety of cosmetics and skincare ingredients, has deferred evaluation of iron oxides because the safety has been assessed by the US Food and Drug Administration. All color additives used in foods, drugs, and cosmetics in the United States must be approved by the FDA and listed in the Code of Federal Regulations. The FDA only approves colors after an extensive review of all safety data and publication of the basis for its approval in the Federal Register.
References:Bernstein, E, Sarkas, H, Boland, P, & Bouche, D, 2020. ‘Beyond sun protection factor: An approach to environmental protection with novel mineral coatings in a vehicle containing a blend of skincare ingredients’, Journal of Cosmetic Dermatology, 19(2), 407–415.