A label can protect you only if the label is right
Mustard has a major advantage over many less-regulated food allergens in Britain: it is one of the allergens for which specific food-information requirements apply.
But there is an uncomfortable reality worth establishing first.
Food labels are produced by humans and food manufacturing systems.
And humans and systems sometimes make mistakes.
In November 2025, for example, the Food Standards Agency issued an allergy alert for a Tesco celery, fruit and nut salad because it contained mustard that had not been declared on the label.
Just a month earlier, Morrisons recalled a salad cream because it could contain egg and mustard that were not mentioned on its label.
These examples shouldn't make somebody with food allergy conclude that supermarket labels are worthless. Quite the opposite: regulated labelling is one of the most important protections available to allergic consumers.
The recalls demonstrate the safety system doing another part of its job: identifying a failure, removing affected food and warning consumers.
But they expose an important distinction.
There is declared allergen risk, which is what the packet tells you.
And there is real-world allergen risk, which depends upon what is actually inside the packet.
Usually those two things should match.
When they don't, an allergy alert and product recall can become extremely important.
And mustard has been involved in one of the most extraordinary recent demonstrations of just how complicated the modern food supply chain can become.
In 2024, the UK experienced a major series of recalls involving mustard ingredients potentially contaminated with peanut. The consequences spread across numerous products and brands because one contaminated ingredient could travel through the supply chain and become incorporated into many completely different finished foods.
It is a perfect illustration of something consumers rarely get to see:
A food product isn't merely a recipe.
It is the end of a supply chain.
And understanding that supply chain is going to take us into the next part of this guide.
The mustard that caused a peanut warning
In September 2024, the Food Standards Agency issued advice that, on the face of it, sounded distinctly strange.
People with peanut allergy were advised to avoid foods containing mustard, mustard powder or mustard flour unless they could be confident those products were unaffected.
Mustard had not suddenly become peanut.
The problem was further back in the supply chain.
Mustard ingredients contaminated with peanut had entered the UK food system. The FSA traced the affected mustard ingredients to a producer in India and identified a UK supplier through which they had entered the market. What followed was not simply the recall of a few jars of mustard.
Affected or potentially affected ingredients had already travelled onwards.
They appeared in spice products, seasonings, sauces, dips, ready meals, sandwiches and other foods sold under numerous brands. Recall notices eventually encompassed products as varied as curry powders, pickles, sauces, seasonings, mustard seeds and prepared foods.
One FSA recall notice included macaroni cheese, BBQ beef jerky, Harvester BBQ sauce and Domino's dips.
Another included sandwiches and pasta salads.
Later updates contained products from still more manufacturers and retailers.
The incident is worth understanding because it demonstrates beautifully — albeit uncomfortably — how modern food production actually works.
A packet of food has a family tree
Imagine a company producing a ready-made chicken sandwich.
It buys bread from one supplier.
The chicken may arrive from another.
Mayonnaise may come from a specialist sauce manufacturer.
A seasoning manufacturer may make a spice blend used by the chicken supplier.
That seasoning manufacturer, in turn, buys individual ingredients from importers or wholesalers.
Those businesses may have obtained agricultural commodities from processors thousands of miles away.
So the sandwich sitting in front of you has something resembling a family tree.
Trace its ingredients backwards and they branch repeatedly into other companies, factories, farms, countries and supply chains.
This is why an allergen problem involving one apparently insignificant ingredient can have consequences far beyond that ingredient's retail shelf.
If contaminated mustard powder is sold only as mustard powder, the problem is relatively contained.
But suppose one tonne of that powder is divided between several manufacturers.
One puts it into curry powder.
Another uses it in seasoning.
Another makes a sauce.
Those products are then sold to dozens of other businesses, which incorporate them into hundreds of finished products.
The original ingredient has effectively disappeared into the food system.
Finding it again becomes a tracing exercise.
That is what makes traceability so important in food safety.
Businesses need to know where ingredients came from and where affected products went, so that when something goes wrong the chain can be followed forwards and backwards.
The 2024 mustard incident provides an unusually vivid example because the danger wasn't principally to mustard-allergic consumers.
It was to peanut-allergic consumers encountering peanut where peanut should not have been.
And it teaches a broader lesson:
Allergen safety isn't just about recipes. It is also about supply chains.