But — and here is the big piece of the puzzle — washing the eggs also cleans off a thin, protective cuticle devised by nature to protect bacteria from getting inside the egg in the first place. (The cuticle also helps keep moisture in the egg.)

With the cuticle gone, it is essential — and, in the United States, the law — that eggs stay chilled from the moment they are washed until you are ready to cook them. Japan also standardized a system of egg washing and refrigeration after a serious salmonella outbreak in the 1990s.

In Europe and Britain, the opposite is true. European Union regulations prohibit the washing of eggs. The idea is that preserving the protective cuticle is more important than washing the gunk off.

At most American farm stands and farmers’ markets, eggs are sold unrefrigerated. And many cooks store unwashed eggs from small producers on their counters, washing them just before they use them — or not at all, if they are getting dropped into boiling water.

However, if you buy farm eggs chilled, it’s better to keep them chilled. Bringing them to room temperature if you’re not going to cook them right away can cause condensation, which can damage the cuticle or encourage mildew. A refrigerated egg, no matter the source, will be good for four or five weeks. Unrefrigerated eggs are best used within a week, though they may be fine for two.

Safety concerns aside, room-temperature eggs perform better in the kitchen. If cold eggs are worked into batters with a high fat content, they can reharden the fats, and you’ll end up with batter that looks curdled and whose texture could be impacted. Also, if you want more volume when you whip egg whites for meringue or soufflés, use room-temperature eggs.

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