What E172 actually is
Iron oxides provide the black in liquorice-style coatings, the red-brown in some cake decoration, and the colour on olives treated to look black. They are the same class of compound as rust, which sounds alarming and is chemically accurate but says nothing about safety, since the food-grade material is purified to a strict specification.
What it is made from
Manufactured synthetically to a controlled purity rather than mined, precisely so that heavy-metal contaminants can be kept within specification.
Vegan, vegetarian, and halal status
Iron oxides are mineral compounds with no plant or animal origin, so they suit every dietary requirement.
Is E172 safe?
Iron oxides are permitted in the EU, UK, and US. EFSA re-evaluated them in 2015 and could not confirm a numerical intake limit, asking instead for better data on particle size and on how much iron is actually released. They remain permitted. The practical point is that these pigments are poorly soluble and largely pass through unabsorbed, so they do not contribute meaningfully to iron intake. The purity specification exists to control heavy-metal contaminants, which is the reason the additive is synthesised rather than mined.
- Poorly soluble and largely unabsorbed, so they do not contribute meaningfully to iron intake
- EFSA asked for better particle-size and iron-release data in its 2015 re-evaluation, and no numerical limit is currently set
- The purity specification exists to control heavy-metal contaminants
Where regulators stand
- EFSA (EU)
- Re-evaluated in 2015. No numerical acceptable daily intake established pending better data on particle size and iron release. Remains permitted.
- FDA (US)
- Synthetic iron oxide is permitted for specified uses including sausage casings and some confectionery.
Foods it turns up in
- Cake and confectionery decoration
- Black olives treated to darken them
- Some coated confectionery
- Tablet and capsule coatings
Names it hides behind
- E172
- Iron oxides and hydroxides
- Iron oxide black, red, or yellow
- Colour (E172)
Common questions
- Is E172 really rust?
- Chemically it is the same family of compound, but the food-grade material is synthesised to a controlled purity specification rather than scraped off metal. The comparison is accurate and not informative about safety.
- Does E172 give me iron?
- Not meaningfully. These pigments are poorly soluble and largely pass through unabsorbed, which is also why no intake limit is set on nutritional grounds.
- Is E172 vegan and halal?
- Yes. It is a mineral compound with no plant or animal origin.
- Why are black olives black?
- Many are green olives darkened with an oxidation process, and iron compounds are used to fix that colour. Naturally ripened black olives are a different product.
- Why is it synthesised rather than mined?
- So heavy-metal contaminants present in natural ore can be kept within the food-grade specification.
Checking a real pack
This page answers the code. The pack in your hand is what decides, because the same code can come from different sources depending on the manufacturer. LabelWise, formerly SafeChoice, scans the label and explains what is in front of you.
LabelWise content is educational and describes how additives are made, regulated, and labelled. It is not medical, dietary, or religious advice. For certification questions, the mark on the pack and the certifying body are the authority.