Is E133 in the Southampton Six?

No. The 2007 Southampton Study tested six dyes — E102, E104, E110, E122, E124 and E129 — and the UK FSA warning label rule applies only to those six. E133 (Brilliant Blue FCF) is a synthetic triarylmethane dye approved in the UK without the Southampton warning.

What foods contain E133?

E133 is found in blue sweets, sports drinks, blue cocktail mixers, ice cream, ice lollies, cake decorations, some tinned mushy and processed peas (to make them greener), and blue-coloured medicines.

E133

Brilliant Blue FCF

Last reviewed: 11 May 2026

Synthetic blue triarylmethane dye — not part of the Southampton Six

On a UK label

E133 is a synthetic blue dye that does not carry the FSA Southampton warning. The Southampton Study tested six other dyes — E102, E104, E110, E122, E124 and E129. E133 is regulated under standard EFSA additive rules instead, with an ADI of 6mg/kg body weight per day.

What is E133?

E133 is Brilliant Blue FCF, a synthetic bright-blue triarylmethane dye derived from petroleum chemistry. It's not an azo dye like most of the Southampton Six — the chemistry is structurally different, which is part of why the regulatory position differs.

Also known as: FD&C Blue No. 1 (US name), Acid Blue 9, CI 42090, Blue 1.

It's used because it's water-soluble, very stable, and gives a strong blue tone that pure natural blue pigments (e.g. spirulina, butterfly pea) struggle to match for shelf-life. It's commonly blended with E102 Tartrazine to create the green tone in tinned mushy and processed peas.

Where you'll see E133 on a UK label

Sweets and confectionery

Blue sweets — gummies, jelly beans, blue M&Ms and Smarties
Iced and decorated cakes
Some sherbet

Drinks

Blue-coloured sports and energy drinks
Blue cocktail mixers (blue curaçao replicas)
Some flavoured cordials

Other foods

Ice cream and ice lollies
Tinned mushy and processed peas — blended with E102 to make green
Cake decorations and writing icing
Coloured-piece breakfast cereals

Non-food uses

Coloured pills and liquid medicines
Mouthwash
Shampoos, soaps, cosmetics

What the science shows

Not in the Southampton Study

The 2007 Southampton Study tested six dyes — E102, E104, E110, E122, E124 and E129. E133 was not in that study, and is not covered by the FSA warning label rule. Pages that group it with the "Southampton Six" are repeating an error.

Aspirin and NSAID cross-reactivity

The clinical literature describes urticaria and asthma symptoms in a small number of aspirin-sensitive individuals after E133 exposure, similar in pattern (though not in mechanism) to the azo-dye cross-reactivity seen with the Southampton Six. Reported reactions include hives, rhinitis and bronchoconstriction in people with aspirin-induced asthma.

Gut absorption

E133 is poorly absorbed from the gut — most passes through unchanged. Small amounts absorbed are excreted in urine (and can colour it blue or green at high single doses). There's no evidence of accumulation.

Mast-cell and intravenous concerns (medical context only)

Case reports describe systemic reactions to E133 when used as a tracking dye in enteral feeds in intensive-care patients — a medical-use context rather than a dietary one. This led the US FDA to issue a 2003 advisory restricting that specific clinical use. It does not apply to E133 in food.

Regulatory status

UK / EU: approved with an ADI of 6mg/kg body weight per day. No Southampton warning required — E133 is not one of the six dyes covered by the rule.

US: FDA approved as FD&C Blue No. 1.

Australia: approved (Code 133).

Who has the strongest reason to avoid E133

People with aspirin or NSAID intolerance — case reports of cross-reaction
People with chronic urticaria — case reports of worsened hives
Anyone reactive to other synthetic dyes

Blue and green alternatives on UK labels

Manufacturers replacing E133 typically reach for plant- or algae-derived colours:

Spirulina extract — blue-green from blue-green algae
Butterfly pea flower extract — natural blue, pH-shifting
Anthocyanins (E163) — purple-blue from red cabbage at certain pH
Chlorophylls (E140, E141) — for green replacement of the E102+E133 blend

Reading a UK label

Look for "E133", "Brilliant Blue FCF", or "colour: E133" in the ingredient list. Unlike the Southampton Six, there's no mandatory FSA warning sentence next to the ingredients — but on a green product, E133 is often present alongside E102 (Tartrazine), which does carry the warning.

Track E133 with NutraSafe

Scan UK barcodes to spot E133 — and the Southampton Six dyes it often appears with — in seconds.

Get NutraSafe on the App Store

Last updated: 11 May 2026