Nutrition Diet: How can you tell if eggs have gone bad?

October 25, 2025 •

4 min read

Americans consume over 280 eggs per person annually, making it crucial to know how can you tell if eggs have gone bad to prevent food waste and illness. Knowing the signs of spoilage helps ensure your meals are both nutritious and safe to eat.

Quick Summary

This guide covers reliable methods, including the float, sniff, and visual tests, to help you determine if eggs are spoiled or simply older. It details what to look for, the science behind the tests, and explains safe egg storage practices.

Key Points

The Float Test: Very fresh eggs sink and lie flat. If an egg stands on its end, it's older but likely still safe. If it floats, it's a sign of significant age and should be discarded.
The Sniff Test is Most Reliable: A strong, sulfurous odor is the definitive sign of a rotten egg. If it smells off, toss it, regardless of other test results.
Look for Discoloration: When cracked, an egg white with a pink, green, or iridescent hue is a sign of bacterial contamination. Discard it immediately.
Observe Yolk and White Consistency: Fresh eggs have a high, firm yolk and a thick, tight white. Older eggs have a flatter yolk and a runny, watery white.
Store Properly for Longevity: Keep eggs in their original carton in the main section of the refrigerator to protect them from temperature fluctuations and odors.

Navigating Freshness Beyond the Date on the Carton

For many, the expiration or 'best by' date on an egg carton is the final word on an egg's safety. However, with proper storage, refrigerated eggs can remain safe to eat for several weeks past this date. The date primarily indicates peak quality, not a hard-and-fast safety deadline. This is especially true for pasteurized eggs sold in the U.S. and other regions with similar handling standards. Learning to trust your senses with a few simple tests is the most effective way to judge an egg's condition.

The Float Test: A Simple Submersion Test

This is a classic and easy way to gauge an egg's age without cracking the shell. The test relies on the fact that eggshells are porous. As an egg ages, it loses moisture and takes in more air, causing the air pocket inside to grow. This increase in buoyancy directly correlates with its age.

To perform the float test:

Fill a bowl or a large glass with enough cold water to fully submerge the egg.
Gently place the egg into the water.
Observe its position in the water.

Here’s what the results indicate:

Sinks and Lies Flat: The egg is very fresh and at its peak. There is very little air inside.
Sinks but Stands Upright: The egg is older but still safe to eat. The air pocket has grown, causing the larger, blunter end to tilt upwards. These eggs are often perfect for hard-boiling, as they are easier to peel.
Floats: The egg is past its prime and should be discarded. The internal air pocket has become large enough to make the egg fully buoyant. While not a definitive indicator of spoilage, it's a strong sign the egg's quality has deteriorated significantly.

The Sniff Test: The Most Reliable Method

Your nose is the most dependable tool for detecting genuine spoilage. Even if an egg passes the float test, it can still harbor bacteria. The classic 'rotten egg' smell is caused by hydrogen sulfide and is a clear indicator that the egg is spoiled.

To perform the sniff test:

While still in the shell: Hold the egg near your nose. A very rotten egg may emit a faint, sulfurous odor even through the shell.
After cracking: If there is no smell through the shell, crack the egg onto a clean plate or bowl—not directly into your recipe. This prevents a bad egg from contaminating other ingredients. A rotten egg will have a powerful, unmistakable odor. If it smells normal, it's a good sign it’s safe to use.

The Visual Test: What to Look for After Cracking

Once cracked, an egg's appearance can tell you a lot about its age and condition. This test complements the sniff test, as some bacteria that cause foodborne illness like Salmonella are odorless.

When you crack an egg onto a flat surface, examine the following features:

Yolk: A fresh egg will have a round, firm, and high-standing yolk. In older eggs, the membrane around the yolk weakens, causing it to flatten and spread out more.
Egg White (Albumen): The white of a fresh egg should be thick and cling closely to the yolk. It may also appear cloudy. As the egg ages, the white becomes thinner and runnier, spreading out more widely. A pink, green, or iridescent white is a sign of spoilage from Pseudomonas bacteria and should be discarded immediately.

Comparing Egg Freshness Tests


Test Method	Reliability for Spoilage	Cracking Required?	What It Indicates
Float Test	Indicates age, not definitive for safety.	No	Age via air cell size. Floaters are old, but may still be safe with further checks.
Sniff Test	Highly reliable for detecting spoilage odors.	Preferably (onto a separate bowl)	Presence of sulfur-smelling bacteria.
Visual Test	Reliable for appearance changes.	Yes	Quality, age (runny white, flat yolk), and visible contamination (discoloration).
Shake Test	Moderately reliable.	No	Sloshing indicates thinning white, suggesting age.

What Happens if You Eat a Bad Egg?

Consuming a rotten egg contaminated with spoilage bacteria can cause gastrointestinal distress, including nausea, vomiting, and diarrhea. However, the more serious risk comes from foodborne pathogens like Salmonella, which can be present in eggs even if they show no signs of spoilage. Symptoms of Salmonella poisoning typically appear within hours to a few days and can be severe, especially for vulnerable populations. Cooking eggs thoroughly is the best defense against Salmonella.

Factors Affecting Egg Shelf Life

Beyond the passage of time, several factors influence how long an egg remains fresh:

Temperature Consistency: Storing eggs in the refrigerator's main body, rather than the door, protects them from temperature fluctuations and helps preserve their quality for longer.
Protective Bloom: In many countries (including the U.S.), eggs are washed to remove a natural protective layer called the 'bloom'. This is why U.S. eggs must be refrigerated, while unwashed eggs in Europe can be stored at room temperature for a shorter period.
Carton Storage: Keeping eggs in their original carton helps shield them from absorbing strong odors from other foods through their porous shells.
Cracked Shells: Any egg with a crack in its shell should be discarded immediately, as the crack allows bacteria to enter and multiply.

Conclusion: Don't Waste, Test!

Knowing how can you tell if eggs have gone bad is a valuable skill for any home cook. By combining the float, sniff, and visual tests, you can accurately assess an egg's freshness and safety, often saving perfectly good eggs from being needlessly discarded. Proper storage is your first line of defense, but when in doubt, trust your senses. A simple float test can give you an initial idea, but the smell test after cracking is the ultimate indicator of spoilage. By following these easy steps, you can confidently and safely incorporate this nutritious ingredient into your diet, reducing food waste along the way. For more detailed information on egg safety, visit the USDA Food Safety and Inspection Service website.

Frequently Asked Questions

The float test works because as an egg ages, its shell becomes more porous, allowing moisture to escape and air to enter. This causes the internal air pocket to expand, making the egg more buoyant.

A bad egg will give off a distinct, putrid, sulfurous odor due to contamination by bacteria. If you notice this smell, throw the egg away immediately.

Yes, if properly refrigerated, eggs are often safe to eat for several weeks past the 'best by' date. This date indicates peak quality, not a hard expiration. Always rely on the float, sniff, and visual tests to be sure.

The egg white, or albumen, contains proteins that begin to break down over time. As this happens, the white becomes thinner and more watery, causing it to spread out more when cracked.

In most cases, eating a spoiled egg will cause only mild digestive upset. However, if symptoms of food poisoning like fever, vomiting, and diarrhea persist, seek medical attention. The main risk is from bacteria like Salmonella.

No, the float test only indicates an egg's age. Salmonella contamination can occur in an egg regardless of its age and is often odorless and tasteless. Thorough cooking is the only way to eliminate this bacteria.

Yes, older eggs can be fine for baking. Some recipes, like hard-boiled eggs or meringues, even benefit from slightly older eggs. As long as the egg passes the sniff and visual tests, it can be safely used.

For optimal freshness, store eggs in their original carton on the main shelves of the refrigerator. Avoid storing them in the door, where temperature fluctuations occur most often.