The legal floor
In the UK, 'gluten-free' is a controlled legal claim, not a marketing phrase any producer can reach for freely. To use it, a product must contain no more than 20 parts per million of gluten — written as 20ppm. That figure is set in food law and applies across the country; it is not a voluntary guideline that manufacturers can interpret loosely.
What 20ppm means in practice is a very low, measurable threshold — low enough to be tolerated by the great majority of people with coeliac disease, though we would always point anyone managing a medical condition to their own clinician rather than a label. The point here is simply that the claim carries legal weight. A product displaying 'gluten-free' has, by law, been produced to that standard.
What the crossed-grain symbol adds
The crossed-grain symbol — a stylised ear of wheat with a line through it — is something different. It is a certification mark, independently licensed and audited, that sits on top of the legal minimum. Producers who carry it have applied for certification, paid a licensing fee, and agreed to regular checks that their manufacturing processes meet the certifying body's own standards.
Think of the legal claim as the floor and the symbol as a quality mark built above it. A product can be legally labelled gluten-free without carrying the crossed-grain symbol; conversely, you will generally not find the symbol on a product that doesn't also meet the legal threshold. The symbol exists to give shoppers an additional layer of confidence, particularly around factory processes and the risk of cross-contamination — issues that the label alone cannot fully communicate.
For smaller artisan producers, the decision to pursue certification is a real one. The auditing process takes time and carries cost, which is worth knowing when you see a small-batch product that meets the 20ppm standard but doesn't display the symbol. Absence of the mark is not automatically a red flag; it may simply reflect the economics of an independent maker.
The oat question
Oats complicate the picture, and they are worth addressing directly. Standard oats are naturally free from gluten-containing grains, but conventional oat crops are routinely grown in rotation with wheat and processed in shared facilities, which means contamination is common. For this reason, oats labelled as gluten-free must be specifically produced — grown in dedicated fields, handled separately, and tested to confirm they fall below 20ppm.
Even then, some people with coeliac disease react to a protein found in oats called avenin, which is distinct from gluten. This is a separate, individual sensitivity rather than a failure of the gluten-free standard, but it does mean that gluten-free oats and oats that are safe for every coeliac are not the same thing. If oats appear in a certified product, the certification confirms the gluten level — it says nothing about avenin.
Reading the label in practice
When you are buying for someone with a serious sensitivity, a few habits help. Look first for the 'gluten-free' claim itself, which carries legal force. The crossed-grain symbol offers additional process assurance and is worth seeking out for products where cross-contamination during manufacture is a realistic concern — oat-based products and baked goods being obvious examples.
The ingredients list and any 'may contain' advisory are also worth reading alongside the front-of-pack claim. A 'may contain wheat' advisory on a product labelled gluten-free is not necessarily contradictory — it reflects a precautionary disclosure about the production environment rather than a confirmed presence of gluten — but it is information worth having.
For everyday shopping, understanding that two distinct systems are at work — one legal, one voluntary certification — makes the label far less confusing. The 20ppm threshold is the consistent, legally enforceable baseline. Everything else is additional information layered on top of it.
