Action limits or threshold values for allergens are important to determine when it is appropriate to use a precautionary allergen statement.Voluntary Incidental Trace Allergen Labelling (VITAL) has been developed to provide a risk based methodology for food producers to use in assessing the impact of allergen cross contact and provide appropriate precautionary allergen labelling ("may-contain").
Links:
[1] https://www.flandersfood.com/world-class-food-production/chemische-veiligheid
[2] http://www.allergenenconsultancy.nl/in/Training_VITAL_Allergen_Thresholds