Quinoline Yellow (E104): A Southampton Colour and the Skin

Quinoline Yellow (E104) is a bright yellow food colour, one of the 'Southampton Six', that some people with chronic hives find worsens their skin. What it is, who reacts, and where it hides.

What it is

Quinoline Yellow is a synthetic bright-yellow food colour. On labels it appears as Quinoline Yellow, Quinoline Yellow WS (the “WS” means water-soluble), C.I. Food Yellow 13, or E104. Chemically it is a quinophthalone dye, not an azo dye, though it is often lumped in with them because it is one of the six colours from the 2007 Southampton study, the group whose findings led to the UK warning label on foods that contain them.

Who reacts, and how it shows on the skin

For most people Quinoline Yellow causes no problem. In a sensitive minority, particularly people who already have chronic hives (urticaria), synthetic colours like this are linked to itching, hives or a worsening of long-standing skin conditions, often a few hours after eating rather than immediately. It behaves as a pseudo-allergic flare rather than a true allergy, so standard allergy tests usually look normal. People who react to one synthetic colour quite often react to several, so it rarely travels alone.

Where it hides

Brightly coloured sweets and ice lollies, fizzy drinks and squashes, some smoked fish (it is used to deepen the yellow), sauces and desserts, and a fair number of medicines and supplements where it colours a tablet coating. Look for the name or E104 on the label. In the UK and EU, foods containing it must carry the warning “may have an adverse effect on activity and attention in children”.

What to do if you think you react

Keep a short food-and-skin diary and look for a pattern over a couple of weeks before cutting anything out. Because the synthetic colours cross over, if you suspect E104 it is worth screening for the other Southampton colours (tartrazine, Sunset Yellow, Ponceau 4R, carmoisine and Allura Red) at the same time. Naturally-coloured alternatives make a clean swap to test the link, and remember to check medicine coatings, not just food. See a GP or allergist if reactions are frequent or severe.

Check it against your own list

A free database like Open Food Facts lets you look up a packaged product and see its full additive list, including any colours, and Fig is genuinely good for managing a defined eating pattern such as a colour-free trial. These give you broad information rather than a check against your own skin. To check a product against the specific things that make your skin react, a personal-list app like ClearaScan lets you save your triggers once and scan any product, food, medication or cosmetic, against your ingredient guard list, flagging only yours. It also keeps a Reaction Journal so you can tie a flare back to the product that caused it, a shared Care Circle so family can scan for you, and a Trusted Products list. It is currently in early access. (Disclosure: our editor co-founded ClearaScan, and we are not paid to mention the others.)