E538

Calcium ferrocyanide

Limited risk

Anti-caking agent in salt.

Vegan: Yes
Vegetarian: Yes

What it is

A highly effective anti-caking agent used specifically in table salt.

How it is used in food

Prevents table salt from clumping together into a solid block, ensuring it flows freely even in humid environments.

Commonly found in

Table salt
Sea salt
Road salt

Health and safety

Safe at regulated levels. Despite the scary "cyanide" name, the cyanide molecules are so tightly bound to the iron atom that they cannot be released or absorbed by the human body.

Evaluated by EFSA and confirmed safe for use in food at authorized levels.

Regulatory status

Region	Status	Notes
Australia & New Zealand FSANZ	Permitted	Permitted under the FSANZ Food Standards Code.
European Union EFSA / European Commission	Permitted	Authorised for food use under EU regulations (Annex II).
United States FDA (Food and Drug Administration)	Permitted	Authorised for food use by the FDA (often GRAS for standard additives).

Identification on labels

E-number: E538

Worth knowing

The chemical bond between the iron and cyanide is incredibly strong — even stomach acid cannot break it to release toxic cyanide.

Conclusion

While the name sounds alarming, this anti-caking agent is safe at the heavily regulated levels used in table and sea salt. Because the cyanide molecules are tightly locked to the iron atom, they cannot be absorbed by the human digestive system, keeping your exposure well within the limits established by EFSA.

References

INCHEM JECFA Evaluation

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Entry last reviewed 2026-07-28.

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