When you buy eggs from a grocery store or farmers market, they look spotless. “When’s the last time you bought a carton of eggs that didn’t look beautiful?” asks Marisa Bunning, a professor and food safety extension specialist in the Department of Food Science and Human Nutrition at Colorado State University. But before Bunning became a professor, she raised backyard chickens with her family, so she knows better than anyone that eggs are still an ingredient that has come from an animal’s body. Viewed from this angle, it seems like eggs might need washing. So does she recommend it? Here’s everything you need to know.

Farm Fresh Eggs vs. Store Bought

Store-bought eggs look beautiful, Bunning says, because the FDA requires eggs to be washed before they’re sold. “Those eggs are washed in a definitive procedure,” Bunning says. For this reason, she recommends you do not wash eggs purchased from a store or farmers market. “It’s not a good idea, because washing these eggs could actually lead to problems, especially if someone washed their eggs in really hot or really cold water,” she says. “The shell is porous. It’s just extra work and wastes water.” However, backyard eggs are another story. If you have backyard chickens or get fresh eggs from somebody who does, things change. “Consumers aren’t used to eggs from their backyard,” Bunning says. “They’re treating them like they’re the same, but they’re not the same.” Though supremely fresh, backyard eggs may require washing. Eggs from a backyard chicken grower who’s a “good flock tender” with clean nesting boxes may not need to be cleaned, Bunning says. But this isn’t always the case. “If eggs obviously have straw, debris, or manure on them, then you’re going to need to clean them,” she says.

Washing Fresh Eggs

To wash fresh eggs, Bunning recommends using water and an emery cloth or a brush. During cleaning, eggs should not touch bacteria or soil, which could enter the interior egg through its porous shell. Washing water should be warm, but not scalding. Eggs shouldn’t be left in standing water (as, again, unwanted contaminants could enter through the porous eggshell). Finally, an unscented dishwashing liquid can provide some extra cleanliness. In the end, most of the billions of the eggs we consume every year in the U.S. don’t need to be washed. But it’s important to know that some of the best ones do. For more information, check out Banning’s backyard egg safety guide that includes a section on washing.

Do Eggs Need to Be Refrigerated?

Often in the U.S., people idealize the European tendency to leave eggs at room temperature. In places like Italy, eggs might not be refrigerated at the local grocery. They might even appear by the canned food and nonperishables. Why? In Europe, leaving eggs out is more common. Generally, more frequent shopping is part of European culture. People aren’t loading up on 60-egg cartons at bulk stores, meaning supplies are used more quickly. Where ingredient turnover is very fast, people might be able to get away with leaving eggs out for a few days. In the U.S., though, Bunning believes people should be refrigerating eggs. “That’s definitely a yes,” she says. “We’re keeping our eggs longer. To me, there’s no reason not to refrigerate them. And we say treat them like you do with dairy products [except butter, which can be left on the counter]. You don’t leave your milk or yogurt out for a while. Eggs are the same.” She adds that egg whites (the kind leftover from recipes calling for just yolk) can keep in the fridge for four days or the freezer for a year. Europeans and Americans tend to approach eggs differently, but so do the agricultural systems that produce these eggs and the authorities that set rules for them. “There are so many differences between them,” Bunning says. “You just can’t compare the two.” Be sure to keep this in mind when buying eggs, storing, and thinking about washing them.