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Iron Oxides and Hydroxides (E172) — What You Need to Know

Generally Safe(7/10)Synthetic

The score is an eNumbers.org editorial summary, not an official agency rating or medical advice. Start with the regulatory status and primary sources below.

What Is Iron Oxides and Hydroxides?

Iron Oxides and Hydroxides are synthetic inorganic pigments that provide red (Fe2O3), yellow (FeO(OH)), and black (Fe3O4) colors. While iron oxides occur naturally, only purified synthetic versions are approved for food use due to the need to control heavy metal contaminants. They are used primarily in confectionery coatings and decorations.

What Is It Used For?

Used as coloring agents in confectionery, cheese rind, cake decorations, and pharmaceutical pill coatings. The three forms provide red, yellow, and black shades respectively.

Function: Red, yellow, and black food coloring pigments
0.2 mg
Dataset exposure estimate
35 mg
ADI-derived reference (70 kg)
0.6%
of ADI (typical diet)

Exposure figures are population-level references, not personal limits. Actual intake varies by diet, product and jurisdiction.

Regulatory & Editorial Context

📊
Acceptable Daily Intake (ADI)
0.5 mg/kg bw/day
🏛️
Regulatory Status
🇺🇸 USA (FDA): Approved for food use at up to 0.1% by weight of finished food
🇪🇺 EU (EFSA): ADI of 0.5 mg/kg bw/day (as iron), established 2015
⚠️ Key Concerns

Synthetic iron oxides used for food coloring must be highly purified to limit heavy metal contaminants. EFSA set ADI at 0.5 mg/kg bw/day (as iron) in 2015, noting that food-grade iron oxides contain very low levels of iron in bioavailable form. The low ADI is precautionary and based on potential heavy metal impurities rather than iron toxicity. FDA limits use to 0.1% by weight of finished food. Generally considered safe at approved levels.

Editorial context score

eNumbers.org currently assigns Iron Oxides and Hydroxides an editorial context label of Generally Safe with a score of 7/10. This is 1.2 points above the database average for colorings (5.8/10). Dataset reference year: 2015. The dataset's population estimate equals about 0.6% of the listed ADI.

This score is not issued by EFSA, FDA, WHO or another regulator.

Commonly Found In

Confectionery coatingsCake decorationsCheese rindOlivesPill coatingsFish paste
Example brands:
Mainly used in pharmaceutical coatingsSome confectionery manufacturers

Always check the label for E172 or 'Iron Oxides and Hydroxides'

▶Chemical Information
Formula: Fe2O3
Molecular Weight: 159.69 g/mol
CAS Number: 1309-37-1
INS Number: 172
Also known as: E172, Iron Oxide Red, Iron Oxide Yellow, Iron Oxide Black, CI Pigment Red 101, INS 172

Frequently Asked Questions about Iron Oxides and Hydroxides

Current dataset status: FDA — Approved for food use at up to 0.1% by weight of finished food; EFSA/EU — ADI of 0.5 mg/kg bw/day (as iron), established 2015. Reported concerns: Synthetic iron oxides used for food coloring must be highly purified to limit heavy metal contaminants. EFSA set ADI at 0.5 mg/kg bw/day (as iron) in 2015, noting that food-grade iron oxides contain very low levels of iron in bioavailable form. The low ADI is precautionary and based on potential heavy metal impurities rather than iron toxicity. FDA limits use to 0.1% by weight of finished food. Generally considered safe at approved levels. Regulatory status and individual risk are not the same; check the primary sources and permitted conditions of use.

Quick Facts

E-Number
E172
INS Number
172
Category
Colorings
Origin
Synthetic
FDA Status
Approved for food use at up to 0.1% by weight of finished food
EFSA Status
ADI of 0.5 mg/kg bw/day (as iron), established 2015
ADI
0.5 mg/kg bw/day
Dataset Review
2015
Ingredient-level Dietary Notes
Vegan: ✅ YesHalal: ✅ YesKosher: ✅ YesGluten-Free: ✅ Yes

Carriers, processing aids and product certification can change suitability. Verify the final label and certifier.

Quick Links

Disclaimer: This information is for educational purposes only and is not medical advice. Always consult a healthcare professional for health-related decisions.

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Calcium Carbonate (E170)Titanium Dioxide (E171)Aluminium (E173)Vegetable Carbon (E153)