In the UK, a food can only be labelled “gluten-free” if it contains no more than 20 parts per million (20ppm) of gluten, whether it’s a pre-packaged product or something served in catering. That single claim is easy to muddle with two other things you’ll see on the same packet: allergen labelling, which emphasises cereals like wheat, barley and oats in the ingredients list, and voluntary “may contain” warnings about cross-contamination.
I’ve drawn this guide from Coeliac UK and the Food Standards Agency guidance supplied for this article, verified on 22 September 2026. Reading a gluten-free claim, an emphasised ingredient and a “may contain” warning as interchangeable messages is where confusion can creep in, so I want to help you separate them.
What does “gluten-free” mean on a food label?
According to Coeliac UK’s Gluten Free Law guidance, a product may only be labelled gluten-free if it contains no more than 20 parts per million, usually shortened to 20ppm, of gluten. That rule applies to pre-packaged products and food served in catering.
That gives the wording a defined meaning. I wouldn’t translate “gluten-free” into a promise of absolute zero gluten, because that is not what the stated threshold says. Equally, I wouldn’t treat it as a loose description chosen because a food seems likely to fit a gluten-free diet.
Coeliac UK explains that UK gluten-free labelling law derives from assimilated Regulation (EU) No. 828/2014 together with Regulation (EU) No. 1169/2011 on Food Information to Consumers. You don’t need to memorise those names to read a packet. The useful part is knowing that the claim has a legal basis and a specific limit.
My starting question would therefore be simple: does the food actually carry the words “gluten-free”? That establishes whether you are reading this particular claim. It is a different question from asking which allergens appear in the ingredients, or whether there is a separate cross-contamination warning.
I’m keeping those questions separate deliberately. The gluten-free wording tells you about the defined gluten limit. The ingredients list and precautionary wording have their own jobs, which are worth understanding before trying to draw a conclusion from the whole label.
What’s the difference between allergen labelling and a “may contain” warning?
Coeliac UK’s How to read food labels guidance explains that cereals containing gluten are among the 14 allergens that must be emphasised in an ingredients list. The cereals it names include wheat, rye, barley, oats, spelt and khorasan wheat, also known as Kamut.
That emphasis might be bold lettering. The Food Standards Agency’s Allergen labelling for food manufacturers guidance on GOV.UK also gives underlining or a contrasting colour as examples. It says each of the listed allergens must be emphasised every time it appears in the ingredients list.
I’d pay attention to the cereal name itself, rather than look only for the word “gluten”. The guidance identifies wheat, barley and the other named cereals, so those are the words to recognise when reading the ingredients. The emphasis helps you spot them, but the name tells you what has been declared.
A precautionary statement has a different purpose. Coeliac UK explains that wording such as “may contain wheat” or “made on a line handling wheat” is voluntary and indicates that the manufacturer has identified an unavoidable risk of cross-contamination.
The word “voluntary” needs care here. I wouldn’t read it as meaning the warning is unimportant or merely decorative. It describes the status of that precautionary wording, while the warning itself communicates an identified risk.
The Food Standards Agency says precautionary allergen labelling should only be used after a risk assessment shows that the cross-contamination risk is real and cannot be removed through controls such as segregation and cleaning. It should not be used as a blanket caution.
So, when I explain a label, I separate an ingredient declaration from a cross-contamination warning. An emphasised cereal in the ingredients list identifies a declared ingredient. A “may contain” statement addresses the risk described by the manufacturer. Neither piece of wording is simply another way of writing “gluten-free”.
This also means I wouldn’t use the absence of a voluntary warning as a substitute for a gluten-free claim. Those are different pieces of information. If a particular combination of wording leaves you unsure, keep the exact wording to hand when seeking clarification, rather than reducing the question to whether the packet has any bold type.
Why do oats need special care on a gluten-free diet?
Oats are where I’d slow the explanation down, because there are two separate points to understand: contamination and the protein in oats themselves.
In its Oats and the gluten free diet guidance, Coeliac UK says standard oats are typically grown and processed alongside wheat, barley and rye. This creates a contamination risk, which is why it recommends only oats specifically labelled gluten-free for people with coeliac disease.
The practical wording to look for is therefore “gluten-free”, rather than assuming that “oats” alone answers the question. Coeliac UK’s legal guidance confirms that uncontaminated oat products which test at 20ppm gluten or less can also be labelled gluten-free.
There is then the separate question of avenin. Coeliac UK explains that oats contain this protein, which is structurally similar to gluten. Most people with coeliac disease tolerate gluten-free oats without problems, but a small number remain sensitive to them.
I wouldn’t turn either part of that guidance into a rule that fits everyone. It does not say that everybody with coeliac disease must avoid gluten-free oats, and it does not promise that everybody will tolerate them. Keeping both points together gives a more useful explanation than either one on its own.
If you have symptoms, concerns or questions about introducing gluten-free oats, speak to your GP or dietitian. Coeliac UK advises reviewing their use with a health professional if symptoms or concerns arise.
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