Reusable bags can pose a food poisoning risk if they are used to carry raw foods, the Food Standards Agency in the U.K. has warned.The consumer watchdog has updated its guidelines on food safety and reusable shopping bags with advice on using separate bags for raw foods, ready-to-eat foods and household items. It says that even if there is no spillage, wrapped raw foods such as chicken and fish can harbor traces of harmful bacteria on their packaging. It adds that eggs and loose vegetables with soil on can also pose a risk.To reduce the chances of cross-contamination when food shopping, the FSA says consumers should have enough bags to carry raw and ready-to-eat foods separately. "Keep enough reusable bags for raw foods only and don't use the same bags again for ready-to-eat foods or for carrying other household items," the agency advises.The agency also recommends labeling shopping bags, checking for leaks and spillages and putting cotton bags used for carrying raw items in the washing machine to kill any harmful bacteria. The website suggests replacing shopping bags regularly and checking the bag for life policy at retailers, as old or damaged bags may be swapped for free at some supermarkets.The updated guidelines don't mean reusable bags are a bad thing, though. Keeping them clean is important, but their benefit to the environment is worth it.