Last reviewed: 8 May 2026
The earth pigments — red, yellow, black — that often hide behind 'natural colour' on UK labels
If you've scanned a UK product and seen "natural colour" on the label without knowing what's actually doing the colouring, E172 is often the answer. Iron oxides are mineral pigments — chemically the same as rust, ochre, and the red and yellow earth tones that humans have used for art and dyes for tens of thousands of years. They sit in the EU and UK "natural colours" bracket precisely because they are inorganic mineral compounds with a long pre-modern food-and-pigment history. This guide covers what they actually are, how the food-grade material is made, where they appear on UK shelves, and what "natural colour" really means once you read the small print.
E172 is not a single substance — it is a family of three iron-based mineral pigments grouped under one E-number. Each one is a different ratio of iron and oxygen, and each one gives a different colour.
These three pigments are the same materials that produced the red and yellow ochres in cave paintings 40,000+ years ago, and the iron-oxide reds and yellows in pre-industrial pottery glazes, plasters and dyes. The food-additive status of E172 is essentially a modern regulatory codification of an extremely old pigment practice. None of this is exotic chemistry: red and yellow earth, ground fine.
Manufacturers reach for iron oxides when they want a dense, opaque, heat-stable colour. Unlike water-soluble plant dyes, iron oxide pigments do not bleed, fade in sunlight or wash out under heat. That is also why they are widespread outside food — in cosmetics (foundation, mascara, eyeshadow), pharmaceutical capsules, ceramics, and pigmented plastics.
This is the part most shoppers do not realise: E172 can be made two different ways, and the regulation does not care which one a manufacturer uses.
Both routes are E172. Both qualify under EU and UK food-additive law. In practice, food-grade E172 is more often synthesised than mined. The reason is purity: food-grade specifications require very low limits on toxic trace metals — arsenic, lead, mercury, cadmium — and it is much easier to control the trace-metal profile in a controlled synthesis than to refine it out of variable natural ore. Cosmetic-grade iron oxides have looser purity specifications, which is one reason cosmetics-grade pigment cannot be substituted into food.
E172 is not a workhorse general-purpose colourant. Most everyday processed foods that need a colour will use something more colour-intense per gram — synthetic dyes, or other natural extracts like beetroot (E162), paprika (E160c), annatto (E160b) or beta-carotene (E160a). Iron oxides are reserved for places where a manufacturer specifically wants a dense, opaque, pigment-style finish that survives cooking and storage.
Most ordinary UK supermarket foods do not contain E172 at all. If you see it on a label, it is usually either a vegan-meat product, a decorative confectionery item, or a pharmaceutical-style coating.
Because E172 is an inorganic mineral compound with a long pre-modern food-and-pigment history, EU and UK regulation permits it under "natural colour" labelling claims. A pack that lists "natural colour" or "colour: iron oxides" on the front of pack is, legally, telling the truth.
The wrinkle: the food-grade material is usually synthesised industrially from iron sulphate, not extracted from ore. So "natural colour" on a UK label can describe a synthesised mineral pigment that is chemically identical to a natural one — same molecule, same atoms, same crystal structure, but produced in a chemical plant rather than dug out of the ground. This is not deceptive in the regulatory sense; it is how the law defines "natural" for inorganic colourants. It is, however, worth knowing if you assume "natural" implies extracted-from-source.
Manufacturers that want to make a stronger "from natural sources" claim can specifically buy the natural-extracted form, but it is more expensive and harder to source at consistent food-grade purity. Most do not — and they do not have to, because the synthesised material is the same compound.
Iron oxides contain iron, but they are not a useful dietary iron source. The iron is locked into a stable mineral lattice and passes through the gut largely unabsorbed. E172 does not contribute meaningfully to the iron content stated on a nutrition panel, and a product coloured with iron oxides should not be read as "fortified".
This matters because iron fortification of food — added to breakfast cereals, breads, infant foods — uses entirely different compounds. The common ones are ferrous sulphate, ferrous fumarate and ferric pyrophosphate. Those are bioavailable iron salts designed to be absorbed in the small intestine. They are not E172, do not have an E-number in the colour series, and serve a totally different purpose. If a label lists one of those compounds, the iron is meant to feed you. If a label lists E172 or "iron oxides", the iron is colouring the product, not nourishing it.
The "natural colours" bracket on a UK label can be filled by very different things. Iron oxides and the plant-derived natural colourants behave differently in food, which is why a manufacturer picks one over the other.
The other natural colours are mostly water- or fat-soluble dyes that tint a food. Iron oxides behave more like ground pigment — they sit on or in the food as solid particles. So if a manufacturer wants a deep matte black icing, a brown vegan burger surface, or a printed colour design that survives baking, E172 is often the only natural-colour option that will do the job. The plant dyes are picked when a translucent tint is wanted, or when the brand wants a recognisable plant origin on the label.
The European Food Safety Authority published a re-evaluation of E172 in 2015 and set an Acceptable Daily Intake of 0.5 mg/kg body weight per day, expressed as iron. The opinion confirmed continued permitted use, but flagged that high-end consumers — particularly children eating coloured confectionery and decorated biscuits — could approach the ADI when iron from all dietary sources is added together.
In the United States, the FDA permits iron oxide as a colour additive under specific certification rules, with synthetic iron oxide regulated separately from natural-extracted iron oxide. US food use is more restricted than EU and UK use, particularly historically.
On UK and EU labels, E172 may be declared as "E172", "iron oxides", "iron oxide red", "iron oxide yellow", "iron oxide black", or under the specific subtype codes E172(i), E172(ii), E172(iii). All of these refer to the same family.
E172 is purely mineral. There is no animal source involved at any point in either the natural-extraction or the industrial-synthesis route. The pigments are accepted as vegan, vegetarian, halal and kosher by mainstream certifying bodies. This is part of why iron oxides are so common in plant-based meat alternatives: a manufacturer who wants a brown, cooked-looking patty needs a colour that is itself plant-and-animal-free, and iron oxide hits that brief.
Iron oxides are inert mineral compounds and are not a recognised common allergen. There are no published case reports of significant E172-mediated food allergy that we are aware of. People with the iron-overload disorder haemochromatosis sometimes ask whether E172 is a concern; in practice the iron in food-grade iron oxide is very poorly absorbed, so it is not a meaningful contributor to dietary iron load. Anyone managing haemochromatosis should follow the dietary guidance from their clinician — they will be focused on bioavailable iron from meat, fish and iron-fortified foods, not on E172.
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