What it is
CI 77491 is the color index designation for red iron oxide, chemically iron(III) oxide (Fe2O3), the compound responsible for rust-red tones. It is an inorganic mineral pigment that is strongly colored, durable, and inexpensive. In cosmetics it is the common pigment that supplies red and pink tones in foundations, tinted moisturizers, blushes, and tinted sunscreens, where it is often blended with yellow and black iron oxides to build skin-matching shades. In sunscreen formulas, iron oxide pigments also scatter and absorb visible light, including high-energy blue light.
Safety & warnings
Cosmetic-grade iron oxides are described as inert, photostable, and non-reactive, and cosmetic references rate them as non-irritating and non-comedogenic. They retain their color and optical properties through the day and are widely used even in products for sensitive skin. In several markets they are permitted colorants subject to purity specifications.
Origin & sourcing
Iron oxides occur naturally; hematite (the alpha phase of Fe2O3) is a major iron-bearing mineral at the earth's surface. For cosmetic use, the pigment is typically produced and purified to controlled specifications. The compound's reddish-brown color reflects iron in the +3 oxidation state.
History
Iron-oxide pigment has an ancient history as a colorant; iron-oxide-based pigment was used in prehistoric cave art many thousands of years ago. As an industrial pigment, iron oxides are valued for being inexpensive, strongly colored, and durable, and they carry the food-color designation E172.
Questions everyone asks
What is CI 77491?
It is the color index code for red iron oxide, iron(III) oxide (Fe2O3). It is the mineral pigment that gives the familiar rust-red and pink tones in makeup and tinted sunscreens.
Why is iron oxide in my sunscreen?
It tints the product to match skin tone and helps even out coverage. Iron oxide pigments also scatter visible light, including blue light, which UV filters alone do not address.
Is iron oxide irritating?
Cosmetic references describe iron oxides as inert and non-irritating, and they are commonly used in products for sensitive skin.