Commercially sold eggs in the United States are washed and sanitized, often with a chlorine-based solution, to remove Salmonella and other bacteria from the shell surface. The process isn’t about making eggs look white. It’s a food safety measure required by federal regulations, and it fundamentally changes how eggs need to be stored afterward.
What Actually Happens During Egg Washing
When people say eggs are “bleached,” they’re usually referring to the industrial washing and sanitizing step that all USDA-graded eggs go through. At the processing plant, eggs are washed with warm water and then treated with a sanitizing solution. The sanitizer is typically chlorine-based, at concentrations between 100 and 200 parts per million. That’s a very dilute solution, roughly comparable to what’s used in municipal drinking water treatment, and it’s regulated by the FDA.
The warm water temperature matters. Regulations require that wash water be warmer than the egg itself. If cold water hits a warm egg, the temperature difference can create a slight vacuum that pulls bacteria through the shell’s tiny pores and into the interior. Warm water prevents that suction effect.
This process is effective. When researchers tested chlorine-based washes on eggs contaminated with Salmonella on the shell surface, the treatment reduced bacterial counts by roughly 99.999% (about 5 log units). That’s a dramatic drop in the organisms most likely to cause foodborne illness from eggs.
Why Salmonella Is the Target
Salmonella Enteritidis is the specific strain that drives egg safety policy. Even clean, unbroken eggs can carry it, because the bacteria can infect a hen’s ovaries and end up inside the egg before the shell ever forms. That’s an important distinction: washing handles what’s on the outside, but it can’t reach contamination that’s already inside.
To address that internal risk, the FDA’s Egg Safety Rule requires producers with 3,000 or more laying hens to follow a broader set of preventive measures. These include controlling rodents and flies, sourcing chicks from Salmonella-tested flocks, maintaining biosecurity plans, and conducting environmental testing at specific points during the laying cycle. Refrigeration is also mandatory, both on the farm and during transport.
The Trade-Off: Losing the Natural Coating
Every egg leaves the hen with a thin, moist protective layer called the bloom (also known as the cuticle). This coating partially seals the thousands of tiny pores in the eggshell, creating a natural barrier against bacteria. It’s the reason a freshly laid, unwashed egg can sit at room temperature for a reasonable period without spoiling.
Washing strips the bloom away. Once it’s gone, those pores are exposed, and the egg becomes more vulnerable to bacterial penetration from the environment. This is exactly why washed eggs must be refrigerated continuously. Without the cuticle, cold temperatures become the primary defense against bacterial growth. If a washed egg warms up and then cools again, condensation on the shell can actually carry bacteria inward through the now-unsealed pores.
Why Europe Does the Opposite
Most European countries prohibit washing eggs before they reach consumers. This isn’t a lax approach to food safety. It’s a fundamentally different strategy built around preserving the bloom rather than removing it.
The European reasoning is straightforward: if you keep the cuticle intact, the egg has its own built-in protection, and you don’t need to refrigerate it. European eggs sit on store shelves at room temperature, which Americans often find surprising. To make this work safely, European producers focus their Salmonella prevention upstream. Many EU countries vaccinate laying hens against Salmonella, which dramatically reduces the chance the bacteria is present in eggs in the first place. Strict biosecurity measures on farms add another layer of protection.
Neither system is clearly superior. The U.S. approach accepts that eggs will arrive at farms contaminated and cleans them after the fact, then relies on refrigeration to keep them safe going forward. The European approach tries to prevent contamination from occurring and keeps the egg’s natural defenses intact. Both countries have low rates of egg-related Salmonella illness, though they get there by very different paths.
Why American Eggs Are Refrigerated
Refrigeration isn’t optional once eggs have been washed. The entire cold chain, from processing plant to grocery store to your kitchen, exists because the bloom is gone. Breaking that chain, even briefly, creates conditions where bacteria can multiply. This is why you’ll find eggs in the refrigerated section in the U.S. but on an unrefrigerated shelf in Paris or London.
If you buy eggs from a local farmer who doesn’t wash them, the bloom is likely still intact. Those eggs can safely sit on your counter for a period, though refrigerating them will extend their shelf life. Once you wash them yourself, though, the same rules apply: they need to stay cold.
White Shells vs. the Washing Process
One common confusion worth clearing up: the washing process doesn’t make brown eggs turn white. Shell color is determined entirely by the breed of hen. White-feathered breeds like White Leghorns, which dominate U.S. commercial production, lay white eggs. Brown-feathered breeds lay brown eggs. The sanitizing solution doesn’t change shell color. A washed brown egg is still brown. The prevalence of white eggs in American supermarkets is simply a reflection of which breeds the industry favors, not a result of bleaching.