"May contain" labelling: A short guide for healthcare professionals

This is a short guide seeking to explain what is meant by precautionary allergen labelling (PAL) and why it is used, which aims to help healthcare professionals advising their food allergic patients about PAL and how to keep safe when shopping for food and eating out. 

Currently, there is no cure for food allergy, so avoidance of relevant allergens is a crucial component of effective management. 

In food manufacturing, and for foods sold loose (e.g. catering establishments, markets and delicatessens, bakeries and fruit and vegetable sections of supermarkets), where food allergens are present along the food chain, there may be a risk of cross-contamination from allergenic foods present within the environment. This cross-contamination might occur at any point in the food chain from cultivation (growing the food), transport, storage and manufacturing of the food.

Food businesses have a legal responsibility through the Food Safety Act and General Food Law to ensure that foods they serve are safe for all consumers, including those with specific dietary needs. They are required to do all they can to minimise the risk of cross-contamination. Where this is not possible, food businesses may place a statement on the packaging of a prepacked food, a menu or other suitable location if the food is sold loose, warning that products might carry a risk of cross-contamination from a particular food allergen or allergens. The wording of this warning varies, but is commonly known as “may contain” labelling, precautionary allergen labelling (PAL), advisory, alibi or allergy warning labelling.

For the purpose of this guide, we will use the term precautionary allergen labelling (PAL) to mean any sort of allergen warning on a food product.


What does the law say?

European food law (Food Information for Consumers, regulation EU No. 1169/2011) requires 14 major allergens to be declared on the labelling of prepacked foods, and food businesses must provide allergen information on request for loose food (e.g. from catering outlets or at catered events), where these allergens are present as an ingredient. These allergens are eggs, milk, fish, crustaceans, molluscs, peanut, tree nuts, seseame, cereals containing gluten, soya, celery and celariac, mustard, lupin and sulphur dioxide and sulphites. There are different lists in other regions, such as the US.

Many people believe PAL (relating to allergens that might be present due to cross-contamination rather than an ingredient) is required by law, but this is not the case. There is no specific legal requirement under EU allergen labelling laws for food manufacturers, retailers or caterers to warn people of the possible risk of cross-contamination with allergens.

If a product does not carry PAL, this might be because the food company has completed a thorough allergen risk assessment and there is no risk of allergen contamination or it might be because the company had not undertaken an assessment and any risk is unknown. The absence of PAL does not mean there is no risk. Equally, products with PAL might have a significant risk of allergen cross-contamination or there might be no detectable allergen cross-contamination.

The Food Information for Consumers (Consumer Regulation 1169/2011), which became enforceable from 13th December 2014, includes the requirement that, where voluntary PAL is used, it must not mislead the consumer, be ambiguous or confusing and, where appropriate, it should be based on relevant scientific data.

Key challenges for healthcare professionals

Many food allergic patients ignore PAL and assume previous tolerance of products with PAL means their food allergy is mild, leading to increased risk-taking. Levels of allergen cross-contamination are often inconsistent across products with PAL and different batches of the same product.

Uncertainties surrounding PAL, and the risk of a potential food-allergic reaction, can lead to anxiety and have a profound effect on the emotional and psychological well being and quality-of-life of the patient and their family. In some cases, this anxiety can present at a clinical level and patients should be referred for appropriate treatment. Healthcare professionals need to be aware of the psychosocial impact associated with food allergy in order to identify ‘red flags’ that might lead to adverse outcomes.

A key challenge for healthcare professionals is assessing which patients are at high-risk of severe allergic reactions. Although food allergy-related deaths are rare, potentially life-threatening reactions do occur and can affect adversely patients' perceptions of risk as well as quality-of-life. Those who are high-risk of severe reactions might require different advice about avoidance and management to those at low risk. It is important to discuss with the individual or parent possible reasons why they think an adverse reaction has occurred in order to provide more personalised advice on future management.

Which patients may be at high risk?

Most severe allergic reactions occur when the allergen is added as an ingredient and either the consumer or the food provider makes a mistake. In some cases, a consumer might not make their food allergy known to the food provider or the food provider fails to provide the proper information about a product. However, many food-allergic individuals ignore PAL. This may be because they perceive PAL as being used without good reason, e.g. they have eaten the food before without reacting; they are confused by the wording/ phrases used; they feel their food choices are too restricted or they have been advised they can safely eat foods carrying PAL. They might also miss the warning entirely because packaging is over-crowded with mandatory labelling information.

Predicting those who may be at high-risk of severe allergic reactions is challenging, but factors that should be considered include:

  • Age

Young food-allergic adults in their teens or 20s are at greatest risk of fatal food anaphylaxis compared with other age groups. Although this might be due in part to increased risk-taking amongst this age group, research suggests that other physiological factors might also cause this age group to be particularly vulnerable.

  • Health

Food allergic individuals exposed to their allergen(s) when they have an infection or are generally unwell might be at greater risk of a severe reaction. Specific health-related risk factors for severe reactions include: Asthma (poorly controlled asthma is a significant risk factor for severe reactions and the majority of food anaphylaxis-related deaths occur in individuals who have asthma) and cardiovascular disease and/ or antihypertensive medication.

  • Dose of allergen

Individuals react to different amounts of allergen. While anaphylaxis can occur at very low allergen concentrations (traces), most life-threatening reactions are caused by larger amounts of allergen. The relationship between dose sensitivity to allergen and severity is not clear, but available data show those who react to very low concentrations (e.g. milligram) are not necessarily at greater risk of severe reactions.

  • Skin contact and inhalation

There is little evidence to suggest that individuals who react through skin contact with their allergen(s) or inhalation of allergenic proteins, where food is being cooked or served, are at greater risk of severe reactions.

  • Previous reactions

The risk of a future severe reaction cannot be predicted from previous reactions. Although individuals who have experienced a severe reaction might react severely in future, many with a history of anaphylaxis will experience non-anaphylactic reactions with future accidental exposures. Equally, many severe food allergy-related reactions occur in individuals who have had mild reactions previously. 

  • Medication

If a food-allergic individual is taking certain types medication, such as non-steroidal anti-inflammatory drugs (NSAIDs) or medication for indigestion (proton pump inhibitors or PPIs), the risk of a severe reaction might be greater.

  • Food type

Any food can potentially cause anaphylaxis. However, foods most commonly associated with severe reactions are peanut, tree nut, sesame, celeriac, seafood and cows' milk. School-aged children and adults with cows' milk allergy may be at particular risk of severe reactions due to accidental exposure. Many who are allergic to egg and cows' milk are able to tolerate these allergens in baked goods, such as cake or biscuits, but those who react to cows' milk and egg in baked foods are at greater risk of severe reactions.

→ In Southern Europe, lipid transfer proteins (LTPs) are potent allergens and have been known to cause severe reactions to foods, such as peach.

  • Alcohol

Drinking alcohol can make risk-taking more likely and might, therefore, impair allergen avoidance and affect how quickly and effectively individuals respond to symptoms if they have a reaction. Alcohol might also increase the uptake of allergens from the gut.

  • Exercise

Exercising just before or after a reaction can cause the reaction to be more severe.

  • Allergy test results (allergy skin prick test and blood tests) are not useful or reliable indicators of reaction severity. A positive test indicates that an individual is sensitised to the allergen, but not how they will react following exposure if the test results are low.

→ A high result implies the patient is more likely to react to that allergen, but it does not mean they will have a severe reaction.

Factors that may suggest a patient is at lower risk for severe allergic reactions include:

  • Tolerance of well-cooked and processed food (e.g. egg, milk)

Some food-allergic individuals can tolerate certain food allergens such as egg or cows' milk or foods containing these allergens, if they have been processed or cooked. Generally, people who can tolerate these foods are less likely to be at risk of a life-threatening reaction due to low-level accidental exposures.

Cooking other allergens, such as peanuts, tree nuts and fish, does not to reduce the likelihood of these allergens causing a reaction.


  • Pollen food allergy syndrome (PFAS)

In some people, reactions to certain nuts, peanut, fruits or vegetables are thought to be due to pollen-related cross-sensitisation to plant-derived foods. Typically, these individuals experience mild symptoms, such as itchiness and tingling around the lips and in the mouth, in response to the raw food but not the cooked food. However, it is important to remember that these mild symptoms are also frequent in patients who have a more typical allergy to the foods and might be at risk of severe reactions. 

Testing for specific allergen components might help identify individuals whose reactions are due to PFAS.

PAL guidance for patients who are high risk for experiencing severe allergic reactions

If you assess your patient as being at high risk for severe reactions, they should be advised to avoid all products bearing PAL, and prescribed adrenaline auto-injectors and should be shown how to use them. They should be advised to carry these and any other emergency medication with them at all times without exception. If for some reason they do not have access to their adrenaline auto-injectors, they should be advised to take extra care to avoid foods with PAL and avoid eating at catering outlets. 

PAL guidance for patients who are low risk for experiencing severe allergic reactions

If you assess your patient as being at low risk for severe reactions, you may suggest they do not need to be as cautious with PAL foods. However, it is important to remember that some food products carry a very significant risk of high levels of allergen cross-contamination.

Other tips for keeping food allergic individuals safe

Food allergic patients or parents of food allergic children should:

  • Read ingredient lists and packaging thoroughly, even if they have bought the product before: food companies change their recipes or introduce new allergens (and, therefore, new risks) to products have been safe previously

  • Buy from companies they know use PAL responsibly (check websites and, if necessary, contact the company concerned)

  • When buying food sold loose either in a supermarket/ market or catering outlet, tell staff about their allergy and ask to see any written allergen information available; the same applies when eating at catered events (e.g. wedding parties)

  • Encourage food allergic children to ask for their food in restaurants and other food outlets, using an agreed form of words, so that this behaviour becomes automatic

  • Develop a personalised management plan for food allergy that includes a day-to-day strategy and an approach for managing a reaction including knowledge of possible symptoms, and when and how to use an auto-injector.

Products that are high risk for allergen cross-contamination

Because of the way food is made (e.g. on a shared production line), certain products (e.g. confectionery [e.g. chocolate], cereals and desserts) often carry a higher risk of cross-contamination from allergens, specifically milk, nuts and peanuts. Dark chocolate is particularly risky: most plain chocolate has a very high risk of milk contamination and should be avoided by milk-allergic individuals irrespective of whether PAL is present or not.

The only exceptions are where product have undergone a thorough risk assessment by the food company concerned (which might include testing for residual allergenic proteins) and been assessed as having no or negligible risk of allergen cross-contamination.

It is very important to discuss risk with your food-allergic patient and advise on avoidance strategies, based on a thorough assessment. If you are a GP and your patient has multiple or complex allergies, it is vital that you refer them to a specialist allergy clinic and a specialist allergy dietitian.

Threshold levels

For several years, food scientists and clinicians have been working towards an understanding of threshold doses for food allergens, i.e. the lowest concentration that can trigger an allergic reaction in a significant proportion of allergic consumers. Once a threshold dose has been established and validated for each allergenic food, the food industry can make efforts to reduce cross-contamination to below these levels. This should result in fewer, more consistently applied PAL, which should reduce uncertainty and make food allergen avoidance easier. Currently, the absence of internationally agreed threshold levels has resulted in inconsistent application of PAL by the food industry.

Frequently asked questions about PAL

  • Is there a genuine risk of contamination of a particular product or dish and will the allergen always be present in every product purchased?

No. Some allergens, such as nuts or seeds, are 'particulate', which means a piece of nut or seed might be present in one piece of (for example) chocolate but not another. Ingredients, such as milk and milk powder, are usually homogeneous, which means they are dispersed equally throughout the product, so each piece of plain chocolate, for example, is likely to contain the same amount of milk. However, a batch of non-nut chocolate that has been made immediately after a nut chocolate, on the same machinery, has a greater risk of cross-contamination than a batch made at the end of the run. Similarly, a batch of plain chocolate produced immediately after a run of milk chocolate is likely to contain high levels of milk.

Food allergic individuals, therefore, should not assume that a product with a PAL will always be safe.


  • Are products that say “may contain traces” or similar phrases less of a risk than those that say just “may contain”?

PAL is not a legal requirement and there are no legal definitions for phrases. Thus, the wording does not necessarily signify any particular level of risk. A product with “may contain traces” or “produced on a shared production line” might carry just as much or indeed more of a risk than one stating “may contain”.

Key messages:

  1. Poorly controlled asthma is an important risk factor for severe reactions

  3. Patients at high risk of severe allergic reactions should always avoid food with PAL

  5. Food allergic patients should not assume a product with a PAL will always be safe

  7. Absence of PAL does not necessarily mean there is no risk of allergen cross-contamination

  9. Food allergic patients who have been prescribed AAIs should always carry them without exception

  11. Carrying an AAI should not be used as a reason for taking risks


A personalised management plan should be developed, appropriate to age and other factors.


This summary should be used in conjunction with “may contain” guides for consumers with allergies