You might understand why washing meat can lead to dangerous cross-contamination, but the risks are less obvious with eggs. Conor O’Flynn, operations manager of O’Flynn Medical, explains that washing an egg “may actively aid the transfer of harmful bacteria like salmonella from the outside of the egg to the inside of the egg.” When you wash an egg, the natural barriers the shell has can be compromised, “allowing the harmful bacteria to pass into the inside of the egg, giving it a perfect environment to grow.” The bacteria can then make its way to you if you don’t cook your eggs thoroughly enough, as you might with a runny fried egg.

The USDA says that when eggs are laid, they have a natural, protective coating called the bloom, which is the first line of defense against bacteria. The bloom is removed by the commercial washing process. “It is replaced by a light coating of edible mineral oil, which restores protection for long-term home storage of eggs,” the USDA explains. “Extra handling of the eggs in your home, such as washing them, could increase the risk of cross-contamination, especially if the shell becomes cracked.”

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