Should You Refrigerate Eggs? The "Bloom" vs. Salmonella Myth

Q: How much faster do eggs age at room temperature?

Eggs age roughly seven times faster at room temperature than they do in a refrigerator. Leaving an egg on the counter for one day reduces its freshness as much as leaving it in the fridge for a full week.

Q: Why does the US wash eggs but the UK doesn't?

The US focuses on removing surface bacteria (like Salmonella) by washing and sanitizing eggs immediately after they are laid. The UK and EU focus on prevention at the source by vaccinating hens, but they leave the eggs unwashed to avoid potential moisture issues from condensation.

This is how the story goes: In the UK, they don’t wash their eggs, so the protective coating on the shell—the bloom (or cuticle)—is not removed. This supposedly means they don’t have to refrigerate their eggs because they’ll last much longer at room temperature. Meanwhile, in the U.S., we wash our eggs and remove this “magic” layer, making refrigeration mandatory.

This is a myth. It is completely unfounded and based on a poor grasp of how eggs actually deteriorate. The egg cuticle does not make an egg a hermetically sealed environment like a tin can. Here is the scientific truth about the bloom and why it doesn’t protect eggs as much as people think.

Quick Summary: Do Unwashed Eggs Need Refrigeration?

The Bottom Line: Regardless of whether eggs are washed or unwashed, refrigeration is the safest and best practice.

The “7x” Rule: Eggs age seven times faster at room temperature than in the fridge. One day on the counter is equivalent to one week of freshness lost.

The Bloom (Cuticle) Myth: While the natural coating (the bloom) provides a slight barrier, it is not a hermetic seal. Salmonella can and does penetrate the shell even if the bloom is intact.

US vs. EU: The US washes eggs to remove surface bacteria; the EU vaccinates hens to prevent it. Both systems have merits, but neither makes room-temperature storage “better” than refrigeration for safety or quality.

Does the Egg Bloom (Cuticle) Prevent Salmonella?

Let’s look at Salmonella. It is possible for an egg to be contaminated with Salmonella. That is why we are advised not to eat raw eggs. An egg can be contaminated with Salmonella in two ways:

1. Internal Contamination (Before the Shell Forms)

An egg can be contaminated with Salmonella while it is still developing inside the hen. This is caused by direct contamination of the egg contents before oviposition and originates from infection of the reproductive organs. There are antimicrobial defense factors in the egg that the bacteria must survive; however, Salmonella Enteritidis (SE) can often survive and penetrate the yolk.

2. By Contamination of the shell and penetration into the egg

An egg can be contaminated when feces is deposited on the egg. Salmonella can also contact the shell while it is being laid when the bacteria is present in the hen’s vagina. Salmonella then gets into the egg by penetration through the eggshell and shell membranes.

Egg Barriers To Bacteria

An egg does possess barriers to bacterial contamination. One barrier is the oft-discussed cuticle. The cuticle is a hydrophobic proteinaceous layer that covers the eggshell and pore openings.

As well, the shell membranes, which consist of three different layers, also provide protection against bacteria entering the egg through the shell. If the egg is contaminated during development, these protections are for naught.

However, despite the egg’s defenses against bacterial penetration, including anti-microbial factors, research has shown that numerous bacteria, including Salmonella, can and do rapidly penetrate into eggs. The egg is especially vulnerable immediately after it is laid. This may be because for at least five minutes after it is laid, the cuticle is immature and some of the eggshell’s pores may be open.

In addition to other factors affecting bacterial penetration, older eggs are also more vulnerable as the egg becomes dehydrated, causing the cuticle to shrink and exposing pores to bacterial penetration.

Although there is still research to be done, it is not even clear that cuticle deposition plays a significant role in whether or not eggs become contaminated. Some research has found no relationship between cuticle deposition and bacterial contamination within the egg.

All this means that the cuticle does not protect an egg from bacterial contamination. So, those who believe that as long as the egg’s cuticle is intact, it is immune to Salmonella penetration and therefore is safe even if stored at room temperature, have been misinformed. In this case, refrigeration would be wise to slow down the growth of bacteria.

This is why we must look at the scientific evidence instead of mechanisms. The notion that not washing the eggs and thus leaving the cuticle intact makes an egg invulnerable relies solely on a mechanistic explanation that is disproven by direct evidence.

How Long Do Unwashed Eggs Last?

All of this is to say nothing of egg aging. Eggs age and change whether or not they are contaminated. The cuticle in no way stops these changes from occurring. Again, direct evidence has shown that eggs stored at room temperature age seven times faster than eggs stored in the refrigerator.

The Reality Check: Store-Bought Eggs Are Not Fresh

It’s easy to look at European room-temperature storage and think we should do the same in the U.S., but there is a major logistical difference: Time.

Most people don’t realize that store-bought eggs in the U.S. can already be up to 2 months old by the time they hit the grocery store shelf. When you add another week in your kitchen at room temperature, that egg is effectively “ancient” in biological terms. Even if the bloom were the “magic shield” people claim it is, it is fighting a losing battle against time.

This logistical lag is one reason why many people have turned to raising their own backyard chickens for truly fresh eggs. However, before you trade your refrigerator for a coop, it’s worth considering the actual costs involved. Is it actually cheaper to own chickens or buy eggs? You might be surprised at the real price of ‘free’ eggs.

The Julian Code Myth: Your Eggs Are Older Than You Think

Many people look at the three-digit “Julian Date” on their egg carton (ranging from 001 to 365) and think they’ve found the “secret” to egg freshness.

Here is the catch: That code only tells you when the eggs were packed, not when they were laid. Producers have a 30-day window to pack eggs after they are laid, and those eggs can sit on a shelf for another 30 days after that. When you realize your “fresh” store-bought eggs might already be 60 days old, the idea that the “bloom” is still protecting them becomes even more absurd.

Read More: Learn how to decode the “secret” egg carton codes here.

The EU’s Egg Regulations are Wrong

In fact, the much-touted EU practice of not refrigerating eggs has been questioned by researchers. Much of the rationale for these regulations depends on the idea that condensation is a huge hazard—a fear that researchers argue is overblown compared to the benefits of precise temperature control.

According to a study published in Trends in Food Science & Technology, the current EU regulations contain several major flaws:

Overemphasis on Condensation: The rules focus heavily on the risk of “damp” eggshells while overlooking more significant safety and quality hazards.
Vague Temperature Requirements: Precise requirements for temperature and humidity are often missing or obscure, leading to confusion for both operators and consumers.
Fear of Chilling: The regulations actually discourage chilled storage and even downgrade eggs to “Class B” if they are refrigerated, despite a lack of evidence that room temperature is safer.
Neglect of Science: The research suggests the EU needs to update its standards to include temperature conditions that actually correlate with safety, quality, and shelf life.

The EU’s egg-handling regulations are frankly, completely, and utterly wrong. They rely on what I call “magical thinking”—the illogical belief that a lack of condensation is more important than the slowed bacterial growth provided by refrigeration.

Washing vs. Quality: What Actually Matters?

While scientists debate exactly how much the washing process affects the bloom, the data is clear on one thing: refrigeration is a much stronger protector of quality than the cuticle itself. (Additional sources, Effect of egg washing on the cuticle quality of brown and white table eggs, Cuticle and pore plug properties in the table egg)

Factor	With Intact Bloom (Unwashed)	Washed & Refrigerated
Bacterial Barrier	Provides a slight physical shield, but is not a hermetic seal.	Surface bacteria removed; cold temps halt internal growth.
Salmonella Risk	Bacteria can still penetrate pores; room temp allows rapid multiplication.	Growth of any present bacteria is effectively “paused” by cold.
Aging Rate	7x Faster (1 day = 1 week in the fridge).	Slowest possible deterioration of whites and yolk.
Moisture Loss	Slowed slightly, but cuticle shrinks over time at room temp.	Minimal; protected by consistent humidity/temp in the fridge.

Factor	With Intact Bloom (Unwashed)	Washed & Refrigerated
Bacterial Barrier	Provides a slight physical shield, but is not a hermetic seal.	Surface bacteria removed; cold temps halt internal growth.
Salmonella Risk	Bacteria can still penetrate pores; room temp allows rapid multiplication.	Growth of any present bacteria is effectively “paused” by cold.
Aging Rate	7x Faster (1 day = 1 week in the fridge).	Slowest possible deterioration of whites and yolk.
Moisture Loss	Slowed slightly, but cuticle shrinks over time at room temp.	Minimal; protected by consistent humidity/temp in the fridge.

How to Store Eggs for Maximum Freshness.

Although refrigerators often come with little egg-shaped indentations in the door for egg storage, it’s not cold enough in the door to store eggs. The best place to keep eggs is on the bottom shelf.

Keep them in a dry carton, and place them with the large side up to keep the egg cell within the egg from migrating toward the yolk.

Don’t wash eggs, even if you see a little dirt (or other stuff) on them. Usually, eggs are coated with a thin coating of oil to help protect them and keep them fresher longer. Washing them is only going to wash off this protective coating.

Frequently Asked Questions About Egg Safety

Does the “bloom” make eggs shelf-stable?

No. While the bloom (cuticle) is a natural protective coating, it is not a hermetic seal. Research shows that bacteria like Salmonella can still penetrate the shell even when the bloom is intact.

How much faster do eggs age at room temperature?

Eggs age roughly seven times faster at room temperature than they do in a refrigerator. Leaving an egg on the counter for one day reduces its freshness as much as leaving it in the fridge for a full week.

Why does the US wash eggs but the UK doesn’t?

The US focuses on removing surface bacteria (like Salmonella) by washing and sanitizing eggs immediately after they are laid. The UK and EU focus on prevention at the source by vaccinating hens, but they leave the eggs unwashed to avoid potential moisture issues from condensation.

Is it safe to eat unwashed eggs that have been left out?

While many countries store unwashed eggs at room temperature, it is not the safest method. Even with an intact cuticle, internal bacterial growth is significantly higher at room temperature. For maximum safety and quality, refrigeration is always recommended.

Is it safe to eat eggs during a bird flu outbreak?

Yes. According to the USDA and CDC, bird flu does not present a food safety risk as long as eggs are handled and cooked properly. The virus is highly sensitive to heat, so thorough cooking (avoiding runny yolks) effectively eliminates any risk. Read my full guide on whether you can get bird flu from eggs here.