Knowing the greatest amount of an allergen they can consume before experiencing symptoms is a difficult but important goal for individuals with food allergy. A recent review by the US Food and Drug Administration and published in the Journal of Allergy and Clinical Immunology highlights the many benefits of understanding allergen thresholds.
As well as informing allergen labelling strategies used by the food industry, knowledge of thresholds might improve quality of life for patients by helping them understand their potential risk for reactions to low level allergen exposures and helping them to make informed choices regarding food. However, determining thresholds for patients with food allergy is a difficult task, not least because the only method available is an oral challenge that might cause a potentially life-threatening reaction. From previous studies, it is also known that individual thresholds can be affected by various factors, such as exercise and infections, and might not be reproducible from one challenge to the next. In addition, they cannot be extrapolated from one individual to another.
Risk assessment approaches are being proposed to estimate thresholds for populations of allergic patients. This approach requires many individual data points on eliciting doses determined using double-blind, placebo-controlled food challenge studies using low-dose allergen protocols. For many of the key allergens there are over 200 such data points which allow mathematical prediction of eliciting doses in 1% or 5% of the population.
One study that aimed to establish thresholds for precautionary allergen labelling purposes demonstrated that the majority of allergic patients might not be sensitive to minute allergen exposures, with more than 70% of patients not expected to react to 60 mg of peanut protein (a dose equivalent to 1 whole peanut).
While there is still much research to be done to determine reliable population thresholds for the main allergens, this review provides a useful summary of the progress that has been made in a relatively short space of time and highlights where further discoveries may be made in the near future.
Reference: Luccioli & Kwegyir-Afful 2014. Journal of Allergy and Clinical Immunology. DOI: http://dx.doi.org/10.1016/j.jaci.2014.05.007