Store-bought eggs must be refrigerated from farm to table. But if they’re fresh off the farm, it’s a different story.

“Commercial eggs are washed at a processing plant,” says Maribel Alonso, a technical information specialist at the U.S. Department of Agriculture. Washing removes dirt and bacteria from the eggs’ shells, she adds, “but it also eliminates the ‘bloom.’”

That’s the natural coating that helps keeps water in and bacteria like Salmonella out.

“The washed shell is porous, so anything on the outside can contaminate the inside,” explains Alonso. Once the bloom is gone, refrigeration keeps Salmonella from growing.

And once eggs have been refrigerated, they need to stay there. A cold egg left at room temperature can “sweat,” which opens the shell’s pores.

But bloom or no bloom, eggs last longer in the fridge.

(To kill Salmonella, cook eggs until both the white and yolk are firm. Like a runny yolk? To lower your risk, try pasteurized eggs, which have been treated to kill Salmonella.)

The bottom line

Refrigerate store-bought eggs.

Photo: Milan/