Smell it. A spoiled boiled egg smells sharply sulfurous or sour and you won’t be uncertain. Also discard any egg that feels slimy or chalky, or shows pink, blue or iridescent colour in the white. The float test only works on raw eggs and tells you nothing about a cooked one. When in doubt, throw it out.
Where this guidance comes from
Storage windows and handling rules follow USDA Food Safety and Inspection Service guidance and FDA advice on egg safety. Nothing here has been shortened or stretched for convenience.
What we haven’t done: no food-safety professional or clinician has reviewed this page, and it isn’t medical advice. If you think you’ve eaten something that made you ill, contact a doctor rather than a website.
The four checks
1. Smell — the one that actually works
Spoiled eggs produce hydrogen sulfide, and the result is unmistakable: sharp, sulfurous, sour, unpleasant in a way that stops you eating before you’ve decided to.
One caveat that confuses people: a freshly boiled egg often smells faintly of sulfur too, especially a hard boiled one. That’s a normal by-product of cooking and it fades. The spoilage smell is sharper and genuinely off, not just eggy.
2. Texture
A peeled boiled egg should be smooth and firm. Slimy or chalky means bacterial growth. Discard it, and don’t taste to check.
3. Colour
Any pink, blue, green or iridescent tint in the white is a stop sign — that can indicate Pseudomonas bacteria.
Not to be confused with the grey-green ring around an overcooked yolk, which is iron sulfide and completely harmless. It’s a cooking artefact, explained in the doneness guide. Ring around the yolk: fine. Colour in the white: bin.
4. Time
The most reliable check of all, because spoilage isn’t always detectable. If it’s been more than a week in the fridge, or more than two hours at room temperature, discard it regardless of how it seems. Write the date on the container — see the shelf life page.
Why the float test doesn’t apply
The float test measures the size of the air cell inside a raw egg. As a raw egg ages, moisture evaporates through the porous shell and the air cell grows, so older eggs float. It’s a freshness indicator — and even for raw eggs it isn’t a safety test. A floating raw egg is old, not necessarily dangerous.
On a cooked egg it’s meaningless. The white is solid, the density has changed, and the result tells you nothing about whether bacteria have grown. Ignore it.
Salmonella, briefly and accurately
Salmonella is the main pathogen associated with eggs. Per FDA guidance, thorough cooking is what eliminates it, and a fully hard boiled egg is cooked through.
Where risk remains. Undercooked eggs — soft boiled, runny-yolk, or raw — don’t reach that threshold, so a small risk persists. For most healthy adults it’s very low with refrigerated, commercially graded eggs. It matters considerably more for people who are pregnant, very young, elderly, or immunocompromised, and pasteurised eggs are the sensible option for anyone in those groups who wants a runny yolk.
Recontamination after cooking is the underrated risk. Cooking removes the shell’s protective cuticle, so a boiled egg left in the danger zone can grow bacteria it picked up afterwards — from hands, surfaces, or the container. This is why the two-hour rule applies to cooked eggs at all.
Symptoms of salmonellosis typically appear 6 hours to 6 days after exposure and include diarrhoea, fever and stomach cramps. Most people recover without treatment, but seek medical care for high fever, prolonged vomiting, signs of dehydration, or symptoms lasting more than a few days — and don’t wait if the person affected is very young, elderly, pregnant or immunocompromised.
Preventing spoilage in the first place
- Refrigerate within two hours of cooking — one hour above 90°F / 32°C.
- Leave them in the shell until you need them. The shell isn’t a barrier any more, but it’s still a good container.
- Back of the fridge, not the door. The door is warmest and swings in temperature.
- Date the container. “Which week are these from?” causes both unnecessary waste and unnecessary risk.
- Don’t refreeze or re-chill eggs that have been out for hours in the hope of saving them. It doesn’t work.
Egg safety questions
How can you tell if a boiled egg is bad?
Smell is the reliable test — spoiled eggs smell sharply sulfurous or sour and you won’t be uncertain. Also discard eggs that feel slimy or chalky, or that show pink, blue or iridescent colour in the white. If it’s been refrigerated more than a week, discard it regardless of how it seems.
Does the float test work on boiled eggs?
No. The float test measures the air cell inside a raw egg, which grows as moisture evaporates with age — it’s a freshness indicator for raw eggs, not a safety test, and it means nothing at all once an egg is cooked.
Why does my boiled egg smell like sulfur?
A faint sulfur smell is normal in freshly cooked eggs, especially hard boiled ones, and fades as they cool. Spoilage smells different: sharper, sour, and unpleasant rather than just eggy. If you’re hesitating over which one it is, discard it.
Can you get salmonella from a boiled egg?
A fully hard boiled egg is cooked through, which per FDA guidance is what eliminates salmonella. Risk remains with soft boiled or runny yolks, and with any cooked egg left in the temperature danger zone long enough to pick up and grow bacteria after cooking.
What is the grey-green ring around the yolk?
Iron sulfide — sulfur in the white reacting with iron in the yolk when an egg is overcooked or cooled slowly. It’s harmless and purely a cooking artefact. Discolouration in the white is a different matter entirely and means the egg should be discarded.
Sources
- USDA Food Safety and Inspection Service — shell eggs and egg products guidance, including refrigerated storage windows and the two-hour rule.
- US Food and Drug Administration — egg safety guidance and salmonella prevention.
- Centers for Disease Control and Prevention — salmonellosis symptoms and typical onset window.
Guidance last checked against source: August 11, 2026.