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‘Too high, too low’: The complexities of using thresholds in isolation to inform precautionary allergen (‘may contain’) labels

The disclosure of ‘priority’ allergens when present as an (intended) ingredient in foods is, in most countries, enshrined in legislation. However, the disclosure of unintended allergen presence (UAP) due to crosscontact or crosscontamination (e.g. through the use of shared production facilities) is not.1 Many food businesses use precautionary allergen (‘may contain’) labels (PAL) to advise consumers as to the possibility of UAP; however, use of PAL is voluntary and not specifically regulated, and the presence/absence of PAL does not inform as to the actual level of risk that a particular food product might pose.2 The use of PAL has significantly increased over the last decade,3 but because of the perception that they are used by food businesses to limit their own legal liability rather than convey useful information to consumers with food allergies and their caregivers, they are frequently ignored.4 Similarly, there is similar variation in interpretation of PAL by healthcare professionals, including allergy specialists.5,6 Most foods with a PAL statement do not contain detectable levels of the identified allergen, whilst some products without a PAL do have UAP, which can pose a significant risk of allergic reaction.3,7 A recent research prioritization exercise, undertaken by the UK Food Standards Agency and involving all relevant stakeholders (including consumers with food allergy, members of the general public, clinicians and researchers, representatives from the food industry and regulatory organizations), highlighted the need to improve use of PAL as a key priority, to allow consumers with food allergy to make informed decisions as to whether a food is ‘safe’ for purchase/consumption.8 In theory, the need for PAL could be informed by ‘action levels’: when the level of potential UAP is above a certain concentration (known as an action level), this would trigger the use of PAL; no PAL would be needed if levels were equal to or lower than this cutoff. Whilst some very dosesensitive people might react to levels of allergen below the action level if a large amount of food containing UAP is consumed, risk could be mitigated in these individuals through risk communication (e.g. patientspecific advice to those who react to smaller amounts of allergen).9 Action levels have been developed based on eliciting dose (ED), the dose (mg) of total protein from the allergenic source predicted to provoke reactions in a defined proportion of the allergic population (e.g. ED05 is the dose predicted to provoke reactions in 5% of the atrisk allergic population). Notably, singledose challenges at an ED05 level of exposure have been used to validate ED05 values for peanut 10 and cow's milk.11 There have been attempts to improve the use of PAL through formal allergen risk assessment,12 for example the Voluntary Incidental Trace Allergen Labelling (VITAL®) scheme established by the Allergen Bureau of Australia and New Zealand.13 However, the current lack of international consensus over use of PAL has led to a variety of regulatory approaches and increasing inconsistency in how food businesses use PAL, even between different member states of the European Union (EU).2 To address this concern, the Codex Committee on Food Labelling, a committee of the Food and Agriculture Organization of the United Nations and World Health Organization (FAO/WHO), is currently evaluating the evidence over improving the use of PAL. In this issue of allergy, Zuberbier et al. report a systematic review in which they sought to assess the number of fatal cases of anaphylaxis to exposures below 5 mg protein for food allergens. They found only 8 cases of fatal anaphylaxis reported in which the level of exposure could be estimated; there were no reported fatalities to levels of exposure below 5 mg protein.14 On the basis of these data, and a reasonable assumption that a portion size of 100 g is more typical than 1 000 g, the authors propose a cutoff of 0.5 mg food protein due to UAP per 100 g food (5 ppm) to inform whether PAL is needed. The finding that no deaths have been reported to exposures under 5 mg protein is useful; however, the number of anaphylaxis fatalities is not a good indicator to define policy with respect to UAP and food safety, to prevent allergic reactions due to UAP. This is partly because more developed healthcare systems may be more effective at managing anaphylaxis, limiting morbidity and mortality. Using a very rare outcome (fatal anaphylaxis, in this case) to a common scenario (unintended allergen exposure) to define public health policy is not a good practice. We, therefore, have significant reservations over some of the proposed suggestions put forward by Zuberbier et al. First, we recognize the allure of a straightforward approach, with a single analytical value applied across all food allergens and for all food product categories. The first iteration of the VITAL® scheme (VITAL1) attempted a similar approach: a ‘trigger’ cutoff or action level (expressed in terms of a single concentration of allergen protein (ppm), independent of the serving size of food), above or below which PAL was or was not recommended.13 The ppm cutoffs were derived from using a food portion of 5 grams (equivalent to one Australian teaspoonful) as the reference quantity. The rationale was that the