You crack an egg into the pan and something smells off. Or you find a carton in the back of the fridge and the date stamped on it passed three weeks ago. Now you have to decide: is this egg still good, or is it bad?
The most reliable way to tell if an egg has gone bad is your nose and your eyes. A spoiled egg has a distinct sulfur or rotten smell the moment you crack it open. The egg white may look thin, watery, or discolored. The yolk can appear flattened or have a greenish or brownish tint. Any of these signs mean you should throw it out.
For an unopened egg still in the shell, you can use the float test as a quick check. A fresh egg sinks in a bowl of water and lies flat on the bottom. An older egg stands upright or floats. Floating does not automatically mean the egg is spoiled, but it does mean the air cell inside has grown large enough that the egg is old and more likely to be bad.
The date on the carton is another useful guide. In the United States, eggs sold at retail are typically marked with a pack date or a sell-by date. These dates are not federal safety deadlines. They are quality indicators. An egg can still be safe to eat after the sell-by date if it has been stored properly and passes the smell and sight test.
What does the float test actually tell you?
The float test measures how much air is inside the egg. It does not directly measure spoilage.
An eggshell is porous. Over time, moisture and carbon dioxide escape through the shell, and air moves in to replace them. The air cell at the wide end of the egg grows larger as the egg ages. A fresh egg has a small air cell, so it sits low in the water. An old egg has a large air cell, so it stands up or floats.
This means the float test tells you the egg’s age, not whether bacteria have moved in. An old egg that floats can still be safe to eat in some cases. A fresh egg that sinks can still be bad if it was cracked or stored improperly.
The float test is best used as one piece of information, not the final word. If the egg floats and also smells bad when you crack it, throw it out. If it floats but smells fine and looks normal, it is very old and the quality will be poor. Some people choose to discard it anyway. That is a reasonable choice.
How can you tell if an egg is bad before cracking it?
You cannot always tell from the outside. Eggshells are designed to protect the contents, and a spoiled egg does not always show visible signs.
That said, there are a few things to check:
- Cracks: A cracked shell lets bacteria in. If the crack happened before you bought the egg, the risk of contamination is higher. Discard eggs with cracks that look old or dirty.
- Powdery or slimy coating: A fresh egg has a natural protective coating called the bloom. If the shell feels unusually slimy or has a powdery white film, it may be past its prime or have been handled poorly.
- Unusual odor before cracking: A rotten egg sometimes gives off a faint smell even before you break the shell. If you notice it, do not bother cracking it.
- Discoloration: Dark spots or a greenish sheen on the shell can indicate mold or bacterial growth.
None of these checks are foolproof. The most reliable test remains your nose after cracking.
What should you look for when you crack an egg?
The moment the egg hits the bowl, you have the best information you will get.
A fresh egg has a firm, round yolk and a thick egg white that stays close to the yolk. As an egg ages, the white becomes thinner and spreads out more. The yolk flattens and the membrane around it weakens.
Signs that an egg is bad include:
- A sulfur smell, rotten smell, or any odor that makes you recoil
- A pink, green, or iridescent tint to the egg white
- A yolk that is discolored, mushy, or has a greenish-brown hue
- Cloudy or bloody egg white (though a small blood spot is normal and not a sign of spoilage)
- Any visible mold or black spots
If you see any of these signs, throw the egg away. Do not taste it to check. Do not cook it and hope the heat kills whatever is wrong. Some bacteria produce toxins that are not destroyed by cooking.
Does the sell-by date on the carton mean the egg is bad?
No. The sell-by date is not a safety deadline.
In the US, the USDA does not require egg cartons to carry a sell-by date. When a date is printed, it is typically a pack date (the day the eggs were washed and packed) or a sell-by date set by the retailer or state. These dates are about quality, not food safety.
According to the USDA, eggs stored properly in the refrigerator can remain safe to eat for three to five weeks after the pack date. That is a general guideline, not a guarantee. How the eggs were handled before you bought them matters. So does how you store them at home.
Refrigeration is important. Eggs left at room temperature age faster and are more vulnerable to bacterial growth. In the US, commercially sold eggs are washed, which removes the natural bloom that protects the shell. That is why refrigeration is recommended. In some other countries, eggs are not washed and can be stored at room temperature, but that is a different production system.
How should you store eggs to keep them fresh?
Store eggs in the refrigerator at 40°F or below. That is the standard food safety recommendation.
Keep them in their original carton. The carton protects them from odors and prevents moisture loss. Do not store eggs in the door of the refrigerator, where the temperature fluctuates each time the door opens.
Do not wash eggs before storing them. If your eggs came from a farm and were not commercially washed, washing them at home can push bacteria through the shell. Commercial eggs in the US are already washed and should be refrigerated.
Use eggs within three to five weeks of the pack date for best quality. If you are unsure how old they are, use the smell and sight test before eating them.
Can you get sick from eating a bad egg?
Yes. Eggs can carry Salmonella, a type of bacteria that causes foodborne illness.
Salmonella infections can cause diarrhea, fever, and stomach cramps. Symptoms usually start six hours to six days after eating the contaminated food and last four to seven days. Most people recover without treatment, but some cases can be severe, especially in young children, older adults, pregnant women, and people with weakened immune systems.
The risk is not just from obviously spoiled eggs. Even fresh-looking eggs can carry Salmonella. That is why food safety agencies recommend cooking eggs until both the yolk and white are firm, and avoiding raw or undercooked eggs, especially for people at higher risk.
A bad-smelling egg is more likely to have high levels of bacteria, but the absence of a bad smell does not guarantee the egg is free of pathogens. Proper cooking is the most reliable way to reduce risk.
What about eggs that have been frozen or hard-boiled?
Frozen eggs can be safe if they were frozen properly. Raw eggs should not be frozen in the shell because the liquid expands and cracks the shell. If you freeze eggs, crack them first and store the raw egg mixture in a sealed container. Frozen eggs can be kept for up to one year, according to USDA guidelines.
Hard-boiled eggs are different from raw eggs. They have a shorter shelf life. In the refrigerator, hard-boiled eggs can be kept for about one week. If they are left at room temperature for more than two hours, throw them out. A spoiled hard-boiled egg may have a sulfur smell, a slimy texture, or a gray-green ring around the yolk (though a green ring can also happen from overcooking and is not necessarily a sign of spoilage).
If you are unsure about a hard-boiled egg, use the same rule: smell it. If it smells wrong, throw it out.
When in doubt, throw it out
That old advice is still the best advice. Eggs are inexpensive. Food poisoning is not.
If an egg smells bad, looks wrong, or has been stored improperly, do not eat it. The float test can tell you the egg is old. Your nose can tell you it is spoiled. When those two signals disagree, trust your nose.
For eggs that pass the smell and sight test, cook them thoroughly and store them properly. That is the most reliable way to enjoy them safely.
Frequently Asked Questions
How can you tell if an egg is bad without cracking it?
You can use the float test: a fresh egg sinks and lies flat, while an older egg stands upright or floats. However, floating only means the egg is old, not necessarily spoiled. The most reliable check is still the smell and appearance after cracking.
Is it safe to eat an egg after the sell-by date?
Yes, often. The sell-by date is a quality indicator, not a safety deadline. The USDA says properly refrigerated eggs can be safe for three to five weeks after the pack date, but you should still check for bad smell or appearance before eating.
What does a bad egg smell like?
A bad egg has a distinct sulfur or rotten smell, often described as similar to rotten meat or spoiled cabbage. If you notice this smell when you crack the egg, throw it away immediately.
Can you get food poisoning from an egg that looks and smells fine?
Yes. Eggs can carry Salmonella even if they look and smell normal. Cooking eggs until both the yolk and white are firm is the most reliable way to reduce the risk of foodborne illness.
