Are School Lunch Bags Bacteria Magnets?

We often think of washing hands as a simple way to prevent the spread of bacteria. A simple rule of thumb for keeping food safe is to keep hot foods hot and cold foods cold. But what about school lunches stuffed in backpacks, stashed in lockers and inside those lunch boxes? Are school lunch bags bacteria magnets? We asked expert Carolyn O’Neil, MS, RD, about food safety when it comes to school lunch boxes.

Carolyn O’Neil, MS, RD:

Make sure your child’s lunch box from home makes the grade for keeping foods safe as well as nutritious. Once a child hops on the bus for school, another three to four hours pass until they dive into their lunch at noon.


Thrown in a locker, stuffed in a backpack or stashed under a desk for several hours, sandwiches and other lunch foods can linger in the bacteria-friendly room temperature “danger zone” of 40 to 140 degrees for too long. Experts advise that perishable foods should not sit out unrefrigerated for more than two hours; in hot weather, 90 degrees Fahrenheit or above, this time is reduced to one hour. This is especially important for schools without air conditioning or those with lockers located outside.


Researchers at the University of Texas in Austin found that 95% of packed lunches were at an unsafe temperature. That’s why insulated lunch bags and boxes with a space to add an ice pack get an “A” from food safety experts.


A simple rule of thumb is to keep hot foods hot and cold foods cold. The food will taste better too, and no food is nutritious until it’s actually eaten.


Many foods are safe to pack without refrigeration. This includes foods such as: peanut butter; breads, bagels and English muffins; dried fruit; fresh fruits and vegetables; nuts and seeds; unopened cans of fruit and pudding; pretzels, popcorn and crackers; and canned and bottled juices.


After lunch, all perishable foods that are uneaten should be thrown away, unless you can keep them at a safe temperature. However, most lunch boxes and cold packs are not designed to keep foods cold for an entire day.


Finally, remember to wash your lunch box every day after use.

Kids Lunch Box” by Renee is licensed under CC BY2.0.