The US produces about 100 billion eggs every year.
And if they're going to be sold on supermarket shelves, the US Department of Agriculture requires companies wash and sanitize them before they get there.
This is to kill bacteria, namely salmonella, so consumers don't get food poisoning.
But it also means that the egg's natural protective coating is washed off. That's why in the US, we have to refrigerate our eggs. (The US Food and Drug Administration recommends storing eggs below 45 degrees Fahrenheit.)
"A cold egg left out at room temperature can sweat, facilitating the growth of bacteria that could contaminate the egg," the Egg Safety Center says on its website. Post-wash, there's not enough of a barrier between the egg and bacteria that forms on the shell. "Refrigerated eggs should not be left out more than two hours."
In Europe, they vaccinate hens to prevent salmonella instead of washing the eggs. So you can keep eggs on the counter there because the protective waxy coating isn't washed off.
If you're worrying whether cold eggs will mess up your recipes, America's Test Kitchen Chef and food science expert Dan Souza told Tech Insider that they've found it doesn't make a difference.
"We debunked the claim that you need to use cold or room temperature eggs for various reasons," he said. "Even if you are making a cake that has a lot of eggs in it, we find that — especially if you’re using a stand mixer — the mechanical action ends up heating things up anyway. So it’s really not a problem.”
But you should make sure you cook eggs to at least 160 degrees Fahrenheit to kill any remaining bacteria.
