If you’re using external suppliers, you need to know what is happening at their sites. Ask them about the allergenic content, what ingredients are affected, and the proportion of the raw material the allergen comprises. Also find out if they process different allergens that may not be part of your product but could cross-contaminate before it gets to you. If you’re in any doubt, presume that their ingredient does have the allergens. Try to make sure ingredients and raw materials are delivered pre-segregated, and don’t be afraid to reject a delivery if there are any signs of cross-contamination.