Plan ahead and first wash your hands before packing a school lunch (or your own).

“Think about the perishability of the foods you’re making,” said Rutgers University professor Don Schaffner, a food scientist and spokesperson for the Institute of Food Technologists. “Perishable foods can remain at room temperature for no more than 2 hours. Properly refrigerated foods can last a long time, but most school children won’t have access to a refrigerator where they can store their lunchbox.”

The Institute offers some guidance for parents as they pack lunches:

•  Start each day with a clean box or bag. Insulated, vinyl lunch bags are popular and do better at keeping foods cool than paper bags or metal lunch boxes.

•  Clean out lunch bags using warm soapy water and allow them to dry completely overnight before packing the next day. This helps deter the growth of bacteria in the bag.

•  Choose secure packing materials, such as sealable, single-use sandwich bags that can be disposed of when used, or reusable plastic wear that is dishwasher safe.

•  As much as possible, opt for foods that are not perishable, such as peanut butter and jelly sandwiches. (Follow the school’s policy on peanut butter. It may not be allowed due to peanut allergies.) PBJs will last from the time you prepare it in the morning until lunchtime. Single-serve fruits in prepackaged containers are also great options because they’re less perishable.

•  Encourage older kids to assemble lunch on their own at school. Pack bread in one container and place fillings like meat or cheese separately with a cold pack. Having kids assemble the sandwich at lunchtime ensures the freshest possible results!

•  Cold packs are designed to keep foods and drinks cold, not cool them down. If you start with room-temperature ingredients in the morning, it’s unlikely the cold pack will be able to cool them enough by lunchtime. Instead, refrigerate items the night before.

•  Always use a cold pack when you are packing anything perishable, like cheese and meat slices or fresh-cut fruit with a yogurt-based dip. Place the perishable food right against the cold pack in the bag.

•  For hot foods like chili, soup, or stew, use an insulated container. Before storing the food, fill the container with boiling water, let it stand for a few minutes, empty it, and then add the hot food.