The neutropenic diet is an eating plan for people with weakened immune systems to limit exposure to harmful bacteria. It involves avoiding raw and undercooked foods and foods from restaurants, and practicing proper food safety in storage, preparation, and hand washing. The basic principles are to avoid foods more likely to contain microbes, properly store and prepare foods to prevent bacterial growth, and limit leftovers to no more than 48 hours. Following this diet can help prevent foodborne illness for those with weakened immune systems such as cancer patients undergoing chemotherapy or stem cell transplants.