Background: Precautionary Allergen ("may contain") Labelling (PAL) is used by industry to communicate potential risk to food-allergic individuals posed by unintended allergen presence (UAP). In 2014, the World Allergy Organization (WAO) highlighted that PAL use was increasing, but often applied inconsistently and without regulation - which reduces its usefulness to consumers with food allergy and those purchasing food for them. WAO proposed the need for a regulated, international framework to underpin application of PAL. In 2019, the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) of the United Nations convened an expert consultation to address the issue of PAL, the outputs of which are now being considered by the Codex Committee on Food Labelling (CCFL).

Objectives: To summarise the latest data to inform the application of PAL in a more systematic way, for implementation into global food standards.

Methods: A non-systematic review of issues surrounding precautionary labelling and food allergens in pre-packaged products.

Results: Approximately, 100 countries around the world have legislation on the declaration of allergenic ingredients. Just a few have legislation on UAP. Given the risks that UAP entails, non-regulated PAL creates inconvenience in real life due to its unequal, difficult interpretation by patients. The attempts made so far to rationalize PAL present lights and shadows.

Conclusions: At a time when CCFL is considering the results of the FAO/WHO Expert Consultation 2020-2023, we summarise the prospects to develop an effective and homogeneous legislation at a global level, and the areas of uncertainty that might hinder international agreement on a regulated framework for PAL of food allergens.