How do you tell if your eggs are contaminated?

According to the Centers for Disease Control and Prevention (CDC), Salmonella is one of the most common causes of foodborne illness in the United States, with a significant number of cases linked to eggs. Therefore, knowing how to tell if your eggs are contaminated is crucial for ensuring food safety and preventing sickness.

Quick Summary

Identify spoiled eggs using the sniff test, visual inspection, and buoyancy tests. Indicators include foul odors, cracked shells, and discolored egg whites. Proper handling and storage minimize risks.

Key Points

• The Sniff Test: A rotten egg will have an unmistakable and strong sulfurous smell. If it smells bad, discard it immediately.

• Visual Inspection: Check the shell for cracks, sliminess, or powdery mold. Once cracked, look for pink, green, or iridescent coloration in the whites or black spots inside.

• Limited Value of the Float Test: An egg that floats is older due to an enlarged air pocket, but it isn't necessarily unsafe. The test measures age, not bacterial contamination.

• Handle with Care: Avoid cracks and proper refrigeration is crucial. Store eggs in their carton in the fridge's coldest section, and wash hands and surfaces after handling raw eggs.

• Cook Thoroughly: The most reliable way to kill harmful bacteria is to cook eggs until both the white and yolk are firm, reaching an internal temperature of 160°F (71°C).

Recognizing Spoilage vs. Contamination

It's important to distinguish between general spoilage and dangerous bacterial contamination. Spoiled eggs are unpleasant but often harmless, while contaminated eggs can cause serious illness, even if they look and smell normal. However, many signs overlap, and when in doubt, it is always safest to discard the egg.

The Most Reliable Test: The Sniff Test

Your nose is one of your best tools for detecting a bad egg. A spoiled egg will produce a strong, foul, sulfurous odor, also described as putrid or funky. This smell is unmistakable and will be present whether the egg is raw or cooked. For the most accurate result, crack the egg into a bowl and give it a good whiff. If it smells off, toss it immediately.

The Visual Inspection: Shell and Contents

Before cracking the egg, examine the shell for signs of trouble. A cracked or broken shell compromises the egg's natural defense barrier, allowing bacteria to enter. A slimy or powdery substance on the shell can indicate bacterial growth or mold. After cracking, inspect the contents. Fresh egg whites are thick and slightly viscous, but a runny, watery white can indicate an older egg. Pink or iridescent egg whites are a tell-tale sign of spoilage from Pseudomonas bacteria. Black or green spots inside the egg are signs of fungal or bacterial contamination and should be discarded. A flattened or discolored yolk is another sign of aging, though not necessarily contamination.

The Float Test: A Tool for Freshness, Not Safety

The float test is a well-known method, but its reliability for detecting contamination is limited. This test indicates an egg's age, not whether it contains harmful bacteria like Salmonella. As an egg ages, its porous shell allows air to enter, causing the internal air cell to enlarge and the egg to become more buoyant.

• How it works: Place the egg in a bowl of cold water. If it sinks and lays flat, it is very fresh. If it stands on its end, it is older but likely still safe to eat. If it floats, it is very old and should be used with extreme caution or discarded.
• Reliability: The float test alone is not a foolproof method for determining food safety. A floating egg may just be old, not necessarily spoiled. Always combine this test with a sniff and visual inspection for the most accurate assessment.

Comparing Methods for Detecting Contamination and Spoilage

Feature	Sniff Test	Visual Inspection	Float Test
Best for detecting	Spoilage, including odor-producing bacteria	Obvious spoilage, shell damage, visible mold or fungus	Relative freshness based on age
Reliability	High for detecting spoilage; poor for pathogenic bacteria	High for visual signs; poor for non-visible pathogens	Low for detecting contamination; moderate for freshness
Main indicator	Foul, sulfuric odor	Discolored whites, cracked shell, slime	Egg sinks (fresh) or floats (old)
Action required	Discard immediately	Discard immediately if cracked or discolored	Proceed with caution; combine with other tests

Proper Handling and Storage to Prevent Contamination

To minimize the risk of contamination, always follow these best practices:

• Purchase eggs from a refrigerated case and check the carton for the USDA grade shield.
• Choose eggs with clean, uncracked shells.
• Store eggs in their original carton in the coldest part of your refrigerator, not the door, where temperatures fluctuate.
• Keep raw eggs and egg products separate from ready-to-eat foods to avoid cross-contamination.
• Wash hands, utensils, and surfaces thoroughly with hot, soapy water after handling raw eggs.
• Do not wash eggs before storing them, as this can force bacteria through the shell.
• Cook eggs until both the yolk and white are firm, reaching an internal temperature of 160°F (71°C), to kill any harmful bacteria.

Conclusion

While a variety of methods can help assess the quality of eggs, detecting contamination can be challenging, as the most dangerous bacteria often do not produce noticeable changes in smell or appearance. The best strategy for ensuring safety is to combine sensory tests (smell and visual) with proper handling and storage practices. Always prioritize caution, especially for vulnerable individuals. If an egg smells off, has a cracked shell, or shows any signs of discoloration or mold, it's safest to discard it. By following these simple guidelines, you can significantly reduce the risk of foodborne illness from contaminated eggs. For additional details on egg safety, visit the American Egg Board's website: https://www.incredibleegg.org/egg-handling-storage-tips/.

References

CDC. (2025, August 28). Salmonella Outbreak Linked to Eggs. CDC.gov. Retrieved October 11, 2025, from https://www.cdc.gov/salmonella/outbreaks/eggs-08-25/index.html. Schaffner, D. (2023, January 24). How to Tell If an Egg Has Gone Bad. Bon Appetit. Retrieved October 11, 2025, from https://www.bonappetit.com/test-kitchen/how-to-tell-if-eggs-are-bad. Open University. (n.d.). 8. Food Contamination and Spoilage: View as single page. OpenLearnCreate. Retrieved October 11, 2025, from https://www.open.edu/openlearncreate/mod/oucontent/view.php?id=194&printable=1. wikiHow. (2025, June 11). 4 Ways to Tell if an Egg is Bad. wikiHow. Retrieved October 11, 2025, from https://www.wikihow.com/Tell-if-an-Egg-is-Bad. Yahoo. (2024, March 12). 11 Signs Eggs Are Not Safe To Eat. Yahoo. Retrieved October 11, 2025, from https://www.yahoo.com/lifestyle/11-signs-eggs-not-safe-153000561.html. YouTube. (2024, April 28). Signs Eggs Are Not Safe To Eat. YouTube. Retrieved October 11, 2025, from https://www.youtube.com/watch?v=YE7bMsApTd4. Food Network. (2023, March 23). How To Tell If an Egg Is Bad. Foodnetwork.com. Retrieved October 11, 2025, from https://www.foodnetwork.com/healthyeats/healthy-tips/2020/02/how-to-tell-if-an-egg-is-bad. YouTube. (2024, August 15). How to Check if Eggs Have Gone Bad | The Key Ingredient.... YouTube. Retrieved October 11, 2025, from https://www.youtube.com/watch?v=PzQ38y_vvdw. Bon Appetit. (2023, January 24). How to Tell If an Egg Has Gone Bad. Bon Appetit. Retrieved October 11, 2025, from https://www.bonappetit.com/test-kitchen/how-to-tell-if-eggs-are-bad. Mill. (n.d.). Can Eggs Expire? How to Know If Eggs Are Safe to Eat. mill.com. Retrieved October 11, 2025, from https://www.mill.com/blog/can-eggs-expire. IoBM. (n.d.). Is The Float Test For Eggs Accurate. IoBM.edu.pk. Retrieved October 11, 2025, from https://ms.iobm.edu.pk/indeks.jsp/open-access/Y64695/IsTheFloatTestForEggsAccurate.pdf. American Egg Board. (n.d.). Important Food Safety Information. Incredibleegg.org. Retrieved October 11, 2025, from https://www.incredibleegg.org/egg-handling-storage-tips/. Consumer Reports. (2025, February 10). Is It Safe to Eat Expired Eggs?. Consumerreports.org. Retrieved October 11, 2025, from https://www.consumerreports.org/health/food-safety/can-you-eat-expired-eggs-a2372837539/. Queensland Government. (2025, September 23). Eggs | Health and wellbeing. Qld.gov.au. Retrieved October 11, 2025, from https://www.qld.gov.au/health/staying-healthy/food-pantry/food-safety-for-consumers/potentially-hazardous-foods-processes/eggs.

Frequently Asked Questions

Can you get sick from eating an expired but non-spoiled egg?

Yes, it is possible. Expired eggs can still carry Salmonella, a bacteria not detectable by sight or smell, even if the egg hasn't noticeably spoiled. Thorough cooking is the best way to reduce this risk.

What is the difference between an egg that is just old and one that is contaminated?

An old egg has undergone natural physical changes, like a thinner white or a flatter yolk, but may still be safe to eat if cooked properly. A contaminated egg, however, harbors harmful bacteria and is unsafe regardless of its age.

Does the color of the yolk or shell indicate safety?

No, the color of an egg's yolk or shell does not indicate its safety. Yolk color depends on the hen's diet, and shell color varies by breed.

How long can eggs be kept after their expiration date?

With proper refrigeration at 40°F or lower, eggs can often last 3-5 weeks beyond the sell-by date. However, this is for quality, not safety. Always check for signs of spoilage before use.

Should you wash eggs before putting them in the refrigerator?

No, you should not wash eggs. Commercial eggs have a protective 'bloom' that keeps bacteria out. Washing can remove this barrier and even force bacteria through the pores of the shell.

Is it safe to eat a floating egg?

A floating egg is older and has a larger air cell, but is not necessarily unsafe. However, since it is very old, you should crack it open and check for any foul odors or unusual appearances before deciding to use it.

What are the symptoms of Salmonella infection from eggs?

Symptoms typically include fever, abdominal cramps, diarrhea, and sometimes nausea or vomiting. They usually appear 6 to 6 hours after consumption and last 4 to 7 days.