Lettuce, raw meat, raw fish and so on often carry bacteria, even pathogenic bacteria, parasitic eggs and so on. Bacteria have been basically killed in baked and cooked food. If raw and cooked foods are mixed, or cooked foods are put in containers filled with raw foods and then cut with knives and chopping boards that have cut raw foods, cooked foods will be polluted. If people eat this cross-contaminated food, it can cause intestinal infectious diseases. Therefore, raw and cooked foods in the family should be placed separately, and knives, bowls, plates and other utensils should be used separately.