The Real Reason Eggshells Should Never Be Put Back In The Carton

Let's face it: It's a whole lot easier to shove your used egg shells back into the carton they came in versus walking them over to the trash, and potentially dripping leftover egg whites along the way. And the subject is more polarizing than you think. You're one or the other — someone who is guilty of doing it or someone who trashes them immediately, and cringes at those that do. Whether this practice is normal is up for debate, but a recent Reddit post brought the subject to light and received an astronomical amount of likes (almost 80,000) and nearly 13,000 comments.

According to Today, the jury seems to be split 50/50, leaving the lingering question of why what seems like half the population feels the need to tuck egg shells back into that styrofoam, plastic, or cardboard carton. Either way you toss it, it's possible that those who recycle their shells and those who trash 'em immediately both have reasonable explanations for their actions. However, the overachieving team may be onto something, as research by Stop Food Borne Illness CEO Mitzi Baum states that keeping broken eggshells in the carton can lead to cross contamination.

Salmonella contaminates the inside and outside of egg shells

Unfortunately, this common practice is not safe. Baum states that eggshells contain salmonella on the inside and outside of the shell. And putting used shells back into the carton increases the risk of contaminating whole eggs with salmonella (Per Today). "Salmonella is the most common pathogen associated with eggs," states Kimberly Baker, Director of Clemson's Food Systems and Safety Program Team. Baker states that when chickens lay eggs, feces contaminates the outside of the shell with the harmful pathogen. Pores of the egg can absorb the pathogen and then contaminate the inside of the egg — or it can be contaminated naturally through the reproductive tract of the chicken. 

Egg Safety states that the transfer of this bacteria can be from our hands, utensils, or even the air. So with risks involved, are you still willing to keep up this habit? Baum says she's never learned of a case where this particular practice has caused someone to fall ill, but adds that there are over 80,000 egg-related illnesses and 30 deaths per year.

Instead of ruling out eggs altogether, small measures can be put into place to keep you and your family healthy — like placing your compost bin or garbage can a little closer to your work space, making tossing them much more convenient, and disposing of egg cartons once all eggs are eaten, as reusing egg cartons can become a reservoir of bacteria (via Egg Safety).