Cross-contamination is a phenomenon that occurs when a food that does not itself contain any allergens is tainted with an allergen during food preparation, cooking, storage, or serving.
Cross-contamination could occur in these and many other settings:
- When food is chopped on a cutting board on which allergens have previously been cut;
- When baked goods are baked on a cookie sheet that hasn't been thoroughly washed after baking cookies containing allergens;
- When foods are cooked on a grill on which foods marinated with allergens are also grilled;
- When spoons on a salad bar are used to serve both allergenic foods and safe foods;
- When knives are used to cut allergenic foods and safe foods without washing in between.