Published Online: November 29, 2012
Recent studies show that a precautionary warning for unintended presence of allergens in foods (so-called “may contain” labelling) on commercially available products is not useful to allergic consumers as the presence or absence of a precautionary warning correlates poorly with the actual presence or absence of the allergen in these products. This leads to frustration because of unnecessary limitation of food choices or can even lead to potentially dangerous situations for allergic patients when they ignore precautionary labelled foods. However, manufacturers of pre-packaged foods cannot reduce such labelling by keeping the amount of allergenic food within safe limits because for most allergenic foods, such limits (the “threshold doses”) within the allergic population are largely unknown.
In an article recently published in The Journal of Allergy & Clinical Immunology (JACI), Blom et al carried out a structured retrospective study to retrieve data on individual lowest doses that elicited allergic reactions to several major allergenic foods. In a cooperation between research organisation TNO and the University Medical Center Groningen, the authors analysed the outcome of double-blind, placebo-controlled food challenges (DBPCFC) which were performed in the pediatric outpatient population of the UMC Groningen in the Netherlands. These food challenges were performed as a routine clinical procedure for the diagnosis of food allergy. For 363 DBPCFCs with seven major allergenic foods with a positive outcome for allergic reactions were selected from the clinical database. For each allergenic food, two population threshold distributions were determined using the individual minimal eliciting dose and the preceding dose of each food challenge based on either objective allergic symptoms as observed by the clinician or any allergic symptom, the latter including both objective and (non visible, patient-reported) subjective symptoms.
Sufficient data were available for peanut (135), cow’s milk (93), hen’s egg (53), hazelnut (28), and cashew nut (31). Fewer children were challenged with soy (10) or walnut (13) and these were insufficient for determination of a population threshold distribution. The authors used these distributions to determine the protein dose at which 5% of the allergic population was likely to have allergic reactions. For objective symptoms this dose was 1.6 mg peanut protein, 1.1 mg cow’s milk protein, 1.5 mg hen’s egg protein, 7.4 mg cashew nut protein, and 0.29 mg hazelnut protein. Thresholds for any allergic symptom were on average 2-6 times lower than for objective symptoms. The peanut threshold distribution for objective symptoms was similar to that previously found in another European centre.
The authors concluded that the threshold distribution curves and ascertainment of protein doses at which a proportion of the allergic population is likely to respond with allergic reactions are a powerful tool to compare different allergenic foods and for informing policy on precautionary labelling. These data will help to develop quantitative guidance on effective use of precautionary labelling.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.