E321 Antioxidant

BHT (Butylated Hydroxytoluene)

Written by the VitaWhat editorial team · Medically reviewed by Steve Davis · Last reviewed 24 July 2026 · Editorial policy

What it does

Antioxidant preserving fats/oils.

How it's made

Synthesised.

BHT (butylated hydroxytoluene) is a synthetic antioxidant closely related to BHA, used to protect fats, oils and fatty foods from oxidation and rancidity, and also employed to stabilise packaging and other materials. It dissolves in fat and works well at high temperatures.

It is made by chemical synthesis from para-cresol (4-methylphenol), which is reacted with isobutylene in an alkylation. Two tert-butyl groups are added to the ring on either side of the hydroxyl group, producing the symmetrical BHT molecule; these bulky groups are what make it such a stable and effective antioxidant.

The product is purified, often by crystallisation, into a white crystalline solid. Like BHA, BHT is used in very small regulated amounts and is frequently combined with other antioxidants and metal-binding agents, the mixture giving stronger and longer-lasting protection than a single antioxidant used on its own.

Possible reactions

Possible allergic and hyperactivity reactions in some; debated safety.

Sources & references

  1. UK Food Standards Agency — Food additives
  2. EFSA — Food additives

Related entries

Ascorbic Acid (Vitamin C)BHA (Butylated Hydroxyanisole)Calcium Disodium EDTAPropyl GallateTBHQ (tert-Butylhydroquinone)Tocopherols (Vitamin E)
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