The short answer is “as far as possible from non-allergenic foods” in a facility that has adequate food safety and allergen control. However, the best practice is to segregate all ingredients and products containing an allergen in a unique warehouse, cooler, or storage area that is solely used for those items.
This helps to eliminate cross contact between allergens and other food in the same facility. It also allows for a more accurate labeling of foods based on their allergen content. Foods that are labelled as ‘free-from’ one or more of the major allergens (milk, wheat, egg, peanuts, tree nuts, fish, shellfish, soybeans) must meet certain criteria to be so labeled. This includes rigorous controls that ensure that the product and its ingredients are truly free of these allergens.
In addition to physical separation of food allergens from other products, the use of distinct utensils for preparation and handling of both non-allergenic and food allergen containing items helps to reduce the risk of contamination. Using the same utensils for both types of food makes it very difficult to clean thoroughly enough to be 100% sure that all allergen residue has been removed.
A thorough training program for all food handlers is essential in reducing the risk of accidental cross contact. This must be ongoing as new employees join the team and to reinforce proper sanitary procedures for existing staff. It is also important to design the layout of facilities in a way that is safe for maintenance staff to move between clean and dirty areas of a plant on a regular basis.