Compendium of the most significant studies with reference to properties, intake, effects.

Voss L, Hsiao IL, Ebisch M, Vidmar J, Dreiack N, Böhmert L, Stock V, Braeuning A, Loeschner K, Laux P, Thünemann AF, Lampen A, Sieg H. The presence of iron oxide nanoparticles in the food pigment E172. Food Chem. 2020 Oct 15;327:127000. doi: 10.1016/j.foodchem.2020.127000.

Montes-Hernandez G, Pironon J, Villieras F. Synthesis of a red iron oxide/montmorillonite pigment in a CO2-rich brine solution. J Colloid Interface Sci. 2006 Nov 15;303(2):472-6. doi: 10.1016/j.jcis.2006.07.064.

Felton LA, Wiley CJ. Blinding controlled-release tablets for clinical trials. Drug Dev Ind Pharm. 2003 Jan;29(1):9-18. doi: 10.1081/ddc-120016679.

Vahur S, Knuutinen U, Leito I. ATR-FT-IR spectroscopy in the region of 500-230 cm(-1) for identification of inorganic red pigments. Spectrochim Acta A Mol Biomol Spectrosc. 2009 Aug 15;73(4):764-71. doi: 10.1016/j.saa.2009.03.027.

Rowe RC. The effect of the particle size of synthetic red iron oxide on the appearance of tablet film coatings. Pharm Acta Helv. 1985;60(5-6):157-61.

Ishikawa Y, Orito S, Oya M. Statistical analysis of washing efficiency for solid particle soil. J Oleo Sci. 2007;56(4):163-8. doi: 10.5650/jos.56.163.

Photos-Jones E, Knapp CW, Venieri D, Christidis GE, Elgy C, Valsami-Jones E, Gounaki I, Andriopoulou NC. Greco-Roman mineral (litho)therapeutics and their relationship to their microbiome: The case of the red pigment miltos. J Archaeol Sci Rep. 2018 Dec;22:179-192. doi: 10.1016/j.jasrep.2018.07.017.

Castro K, Vandenabeele P, Rodríguez-Laso MD, Moens L, Madariaga JM. Improvements in the wallpaper industry during the second half of the 19th century: micro-Raman spectroscopy analysis of pigmented wallpapers. Spectrochim Acta A Mol Biomol Spectrosc. 2005 Aug;61(10):2357-63. doi: 10.1016/j.saa.2005.02.035.

Luna-Bastante L, Gatica-Ortega ME, Pastor-Nieto MA, Vergara-de-la-Campa L, Gómez-Dorado BA, Alonso-Naranjo L, Pérez-Hortet C. Allergic contact dermatitis to Tinosorb S, Scutellaria baicalensis, and other emerging allergens in cosmetics. Contact Dermatitis. 2020 May;82(5):307-309. doi: 10.1111/cod.13460.

 Motolese A, Truzzi M, Giannini A, Seidenari S. Contact dermatitis and contact sensitization among enamellers and decorators in the ceramics industry. Contact Dermatitis. 1993 Feb;28(2):59-62. doi: 10.1111/j.1600-0536.1993.tb03342.x.

CI 77491: properties, uses, INCI functions, safety, alternatives

Red iron oxide – diiron trioxide (predominantly Fe₂O₃, iron(III) oxide)

Synonyms: red iron oxide, Pigment Red 101, E172 (food colorant: iron oxides and hydroxides; often used as a purity reference for cosmetic grades as well)
INCI / functions: colorant

Definition
CI 77491 is an inorganic pigment from the iron oxide family, used as a colorant in cosmetic formulations (make-up and tinted products). From a compositional standpoint, it is primarily associated with iron(III) oxide (Fe₂O₃), responsible for the characteristic brick-red hue and good stability to light and heat. In regulatory databases and technical documentation, the “CI 77491” entry may appear linked to more than one CAS/EC combination because some registries associate the CI denomination with multiple oxides/related forms within the same family, depending on grade and substance registration scope.

Main uses

• Food: as E172 (where applicable by category and purity specification).

• Cosmetics: colorant in make-up and decorative products; often blended with CI 77492 and CI 77499 for skin-tone tuning.

INCI Functions

• Colorant. This ingredient has the function of colouring the solution in which it is inserted in a temporary, semi-permanent or permanent manner, either alone or in the presence of the complementary components added for colouring.

Restricted cosmetic ingredient as IV/135  a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported: Iron Oxide red. Wording of conditions of use and warnings:  Purity criteria as set out in Commission Directive 95/45/EC (E172)

CI 77491 is used in cosmetic products such as blushes, eyeshadows, lipsticks, and foundations due to its rich red color and high opacity.

• Pharmaceutical: potential technical use as a colorant pigment/excipient in selected cases (specification/authorization-dependent).

Industrial Applications

Paints and Coatings: In the paint industry, iron oxide red is used to achieve deep red shades and enhance UV resistance. Its stability and strong tinting properties make it ideal for both decorative and protective coatings.

Plastics and Polymers: This pigment is employed in the production of plastics and polymers to improve color uniformity and opacity. It is commonly used in products like automotive parts, packaging materials, and consumer goods.

Ceramics and Glass: CI 77491 is used in the production of ceramics and glass to achieve stable red colors. It is particularly valued for its resistance to high-temperature processes.

Inks: The pigment is also used in printing inks to produce intense red colors, ensuring high-quality and durable prints.

Identification data and specifications

Key constituents

Functional role and expected performance

Use guidelines (indicative)

Formulation compatibility
CI 77491 is generally compatible with most cosmetic systems, but performance is strongly dependent on dispersion: pigment wetting, deagglomeration, and shear management. In anhydrous systems (sticks, lipsticks), breaking agglomerates is essential to prevent speckling and chromatic non-uniformity; in O/W emulsions and creams, a robust approach is pre-dispersion into the oil phase or the use of predispersions/pigment pastes, with rheology control to prevent sedimentation.

In systems containing polymers and/or electrolytes, pigment loading can alter rheology (apparent viscosity and yield stress). If the grade falls under the EU definition of a nanomaterial, specific compliance and labeling obligations apply; therefore, complete supplier documentation is critical (particle characterization and regulatory status).

Quality, grades and specifications

Safety, regulation and environment
CI 77491 is a permitted cosmetic colorant in the EU via inclusion in Annex IV (CosIng reference). Safety must be assessed on the finished product (use scenario, application area, population, impurity profile). Operationally, the most relevant factors are: control of impurities (trace metals), management of dust during manufacturing (operator protection), and confirmation of nano/non-nano status and full documentary compliance. Environmentally, as a mineral pigment, key impacts relate to dust and industrial effluent management along the supply chain under local regulations.

Formulation troubleshooting

Alternatives

Conclusion
CI 77491 is a red iron oxide (predominantly Fe₂O₃) used as a cosmetic colorant due to stability and reliable performance. Perceived quality in formula depends mainly on grade (purity, particle size, potential surface treatment) and technically correct dispersion (wetting, deagglomeration, rheology), as well as control of impurities and full regulatory/documentary compliance.

Studies

CI 77491 is generally considered safe for use in consumer products when handled according to proper safety procedures. It is important to avoid inhalation of the powder and minimize direct contact with skin and eyes (1). 

Ultraviolet rays from the sun cause skin aging and smartphones emit high-energy visible light from which you should protect yourself. Iron oxides (yellow, red and black) in sunscreens have the property of effectively blocking high-energy visible light especially when combined with zinc oxide (2).

"The Panel on Food Additives and Nutrient Sources added to Food provides a scientific opinion re‐evaluating the safety of iron oxides and hydroxides used as food additives (E 172): yellow iron oxide (FeO(OH)·H2O), red iron oxide (Fe2O3) and black iron oxide (FeO·Fe2O3). Brown Iron Oxide has been included in this assessment for completeness, due to its importance as a commercial blend. The Panel considered that the particle size and particle size distribution should be included in the specifications. In 1980, an ADI of 0‐0.5 mg/kg bw/day was established by JECFA. Absorption of iron from iron oxides is low. The acute oral toxicity of iron oxides is greater than 10 g iron oxide/kg bw. From a subacute and a subchronic toxicity study, the Panel identified a NOAEL for red iron oxide of 1 000 mg/kg bw/day, the highest dose tested. Red (Fe2O3) and black (FeO·Fe2O3) iron oxide, both in nano‐ and micro‐form, were positive in in vitro genotoxicity assays in mammalian cells. Due to the limitations of the database, and considering the impossibility to read‐across between iron oxides with different redox state, the Panel considered that the genotoxicity of iron oxides cannot be evaluated based on the available data. Concerning carcinogenicity and reproductive and developmental toxicity, no signs of toxicity were observed in unpublished studies which were not available and could not be evaluated by the Panel. The Panel concluded that an adequate assessment of the safety of E 172 could not be carried out because a sufficient biological and toxicological database was not available. Refined exposure estimates show that exposure to E 172 ranged from 0.03 mg/kg bw/day for infants to 3.7 mg/kg bw/day for toddlers at the mean and from 0.1 mg/kg bw/day for infants to 9.5 mg/kg bw/day for toddlers at the 95th percentile for the non‐brand‐loyal scenario" (3).

Red iron oxide CI 77491 studies

Molecular Formula : Fe₂O₃

Molecular Weight : 159,69

CAS : 1332-37-2

EC number   215-722-3   215-168-2   257-870-1

UNII   1K09F3G675

Synonyms:

Ferric Oxide Red

Pigment Brown 6

Pigment Brown 7

References_______________________________________________________________________

(1) Aquilina, G., Azimonti, G., Bampidis, V., de Lourdes Bastos, M., Bories, G., Chesson, A., ... & Wester, P. (2016). Safety and efficacy of iron compounds (E1) as feed additives for all species: ferric oxide based on a dossier submitted by Poortershaven Industriële Mineralen BV. EFSA JOURNAL, 14(6), 1-26.

Abstract. The additive under assessment, ferric oxide, contains between 57% and 69% iron (Fe). The EFSA FEEDAP Panel could not conclude on the safety of ferric oxide for the target animals owing to that (i) the application of ferric oxide red is for all animal species, (ii) lifetime administration to animals is not excluded and (iii) a sufficient biological and toxicological database was not available. Regarding (i) the very low absorption of iron from the ferric oxide by target animals and (ii) the homoeostatic regulation of iron metabolism in animals, any influence of feeding the ferric oxide on the iron content of edible tissues and products is not expected. The use of ferric oxide in animal nutrition is unlikely to result in a direct exposure of the consumer to this oxide. Consequently, the supplementation of feed for food-producing animals with ferric oxide would likely not constitute a risk to consumers. Ferric oxide is an irritant to skin and eyes by mechanical action. Owing to the nickel content in the additive, the ferric oxide

(2) 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 Feb;20(2):532-537. doi: 10.1111/jocd.13803. 

(3) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS)
First published: 08 December 2015 https://doi.org/10.2903/j.efsa.2015.4317