E284

Boric acid

Moderate risk preservativesynthetic

Permitted only for caviar in the EU.

Acceptable daily intake: 0.16 mg/kg body weight/day (EFSA)
Vegan: Yes
Vegetarian: Yes

What it is

E284 (Boric acid) is a synthetic preservative. Because it accumulates in the body and poses toxicity risks, its use in food is strictly prohibited across most categories and is legally reserved almost entirely for a single luxury item: authentic sturgeon caviar.

How it is used in food

Preserves sturgeon eggs where no alternative works.

Commonly found in

Genuine sturgeon caviar

Health and safety

Restricted heavily because boron accumulates in the body.

Boron compounds are toxic to the reproductive system if consumed in high doses. While EFSA has established a safe Tolerable Daily Intake, the primary strategy to protect the public from boron accumulation is to ban it in all foods except a luxury item that is eaten in tiny, infrequent quantities.

Reproductive toxicity

general population · evidence: established

Animal studies show that excessive exposure to boron compounds can impair fertility and fetal development. Its strict restriction in food prevents this risk in humans.

EFSA re-evaluation of boric acid and sodium tetraborate

Toxicity occurs through bodily accumulation over time.

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)	Banned	Not approved for use as a food additive. “Banned”

Identification on labels

E-number: E284

How it is made

It is typically manufactured by reacting borax with a strong acid (like sulfuric acid) and crystallising the resulting compound.

Acidification — Borate minerals are treated with strong acids to yield boric acid crystals.

Worth knowing

An old preservative now banned in all EU foods except real sturgeon caviar.

Conclusion

Unless you frequently consume real sturgeon caviar, you will never encounter E284 in your diet. Its approval exists merely to support a highly specific, traditional luxury food industry.

References

EFSA re-evaluation of boric acid and sodium tetraborate — EFSA

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Entry last reviewed 2026-07-28.

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