“May Contain”: What It Means When You’re Intolerant, Not Allergic

By David Hall, founder of IntoleranceLab · Updated August 2026

“May contain milk.” “May contain nuts.” “Made in a factory that also
handles wheat.” These statements are easy to read as a vague ingredient
list. They are not. They are warnings about possible accidental
cross-contact during making, packing or handling.

The most important distinction is between an ingredient that is
deliberately in the food and a precautionary warning. In the UK, the 14
regulated allergens that are intentionally present must be made clear in
the ingredients list. A “may contain” statement is different: it is
precautionary allergen labelling, often shortened to PAL.

What “may contain” actually
tells you

It tells you that the manufacturer has identified a possibility of
unintended allergen cross-contact. It does not tell you that the
ingredient is definitely in every pack. It also does not give you an
amount.

The Food Standards Agency distinguishes required allergen
declarations from voluntary precautionary allergen labelling (PAL). PAL
is information about possible allergen cross-contact, and FSA guidance
says it should be used only where a real risk has been identified that
cannot be sufficiently controlled through measures such as segregation
and cleaning. Food
Standards Agency: allergen declarations and PAL Food
Standards Agency: PAL consultation and guidance

That is why wording varies. You might see “may contain”, “may contain
traces of”, or “not suitable for someone with a peanut allergy”. They
all point to a precaution, not to a recipe ingredient.

Read the ingredients list
first

For someone avoiding a food because it seems to upset their
digestion, the ingredients list is usually the first useful place to
look.

• “Contains milk” means milk is intentionally
  present.
• Milk in bold in the ingredient list means it is
  intentionally present as one of the regulated allergens.
• “May contain milk” means possible accidental
  cross-contact rather than a confirmed recipe ingredient.
• “Dairy-free” or “free-from milk” is a different
  claim and should be read alongside the ingredients list and the
  product’s own guidance.

Check the label each time: recipes and manufacturing arrangements can
change.

The word “each time” matters. A familiar biscuit can have a different
recipe, a new factory or a new warning after a relaunch.

Why this matters more for
an allergy

Precautionary labels are designed around allergy risk. An allergic
reaction can be severe and fast, so a person with a confirmed allergy
should follow the advice of their clinician or allergy team and treat
the label seriously. A home trial is not the right way to decide what is
safe after a fast or severe reaction.

For an intolerance-style digestive pattern, the question is
different. Reactions are often dose-related and can have many possible
explanations. A “may contain milk” warning does not establish that milk
was in your sandwich, or that it explains what you noticed afterwards.
It is a reason to record the product and look at the wider pattern, not
a shortcut to certainty.

That does not mean dismiss the label. It means use it accurately. Do
not confuse it with an ingredient declaration, and do not use a vague
warning to build an ever-longer list of foods to avoid.

A three-step supermarket
label check

Next time you are in a UK supermarket, use this order:

1. Find the ingredient list

Look for the named ingredient first. If you are comparing two
versions of a product, photograph or note the full list rather than
relying on the front-of-pack claim.

2. Find the precautionary
statement

Is it “may contain”, “may be present” or “not suitable for”? Write
down the exact wording and the named allergen. A generic “may contain
nuts” is less informative than a statement naming peanut, hazelnut or
almond.

3. Compare the context

Was the food a new product? Did you eat a large amount? Did it
contain other ingredients you have not considered? Was there alcohol, a
late meal, spicy food, a sauce or a different routine involved? This is
the part a label cannot answer for you.

What not to assume

Avoid four common leaps:

1. “May contain” means it definitely contains the
   ingredient. It does not.
2. No warning means no risk for every person. It does
   not replace reading the actual ingredients.
3. A warning proves the cause of a digestive symptom.
   It does not.
4. A food sensitivity screen replaces label-reading.
   It does not. Labels remain the practical source for what a product
   intentionally contains and for the manufacturer’s precautionary
   information.

The FSA says PAL should not be used where there is no real risk:
unnecessary use can mislead and restrict consumer choice. Food
Standards Agency: international review of allergen-cleaning
guidance

When to get medical help

If a food seems to trigger swelling of the lips, mouth, tongue or
throat, breathing difficulty, trouble swallowing, fainting or a rapidly
worsening reaction, call 999. Do not test the food again.

For persistent digestive symptoms, unintended weight loss, blood in
poo or a bowel change that lasts several weeks, speak to a GP. Take the
product label and a short food diary with you if you can. It gives the
conversation more to work with than a memory of one meal.

The useful rule of thumb

An ingredient list says what the manufacturer intentionally put in
the product. “May contain” is a warning about possible cross-contact.
Both are worth reading, but they answer different questions. Use the
wording carefully, and keep food changes small enough that you can learn
from them.

Related reading: Food Intolerance vs Allergy Guide.