 Not washing your reusable grocery bags after each use can lead to dangerous cross-contamination and make you sick. Over 99% of bags randomly swabbed tested positive for large amounts of bacteria. Some even had coliform or E. coli. Bacteria from shopping carts, conveyor belts, your car, and other foods can transfer to the groceries you're about to eat, putting you at risk of getting sick. To avoid that, try using specific bags for certain products and always wash and store them properly.