Understanding Egg Expiration Dates and How to Safely Use Eggs Past Their Freshness Date

Have you ever found eggs in the back of your fridge and wondered if they are still okay to eat after the date printed on the carton has passed? It's a common situation, and it can be tricky to decide whether to toss them out or use them. Before you waste those eggs or risk an upset stomach, it's helpful to know what the 'expiration date' on egg cartons actually indicates.

In Japan, for example, the date on egg packages is labelled as the "best before date" (賞味期限, shoumikigen), which is not a strict deadline but rather a guideline for when eggs taste their best when eaten raw. This is quite important given the popularity of dishes like raw egg over rice, a cultural specialty there. However, just because the date has passed doesn't automatically mean the eggs are unsafe to consume. The date is more about peak freshness than an absolute cutoff for safety.

Typically, eggs sold in packs are given a best before date of about two weeks from the packaging date. Interestingly, this expiration date is often set shorter than the actual period eggs remain safe to eat. The shelf life of eggs can actually vary significantly depending on how they are stored, especially the temperature at which they are kept.

The main health concern with eggs is the risk of salmonella infection, although eggs are carefully produced and cleaned to prevent it. Even if salmonella bacteria were present inside the egg, they don't multiply rapidly right away. The expiration date is designed to ensure eggs are consumed while still fresh and safe, based on how long it takes for harmful bacteria to start growing rapidly at typical storage temperatures.

The time it takes for harmful bacteria like salmonella to multiply rapidly depends a lot on how eggs are stored. There’s a scientific formula called Humphrey’s theory, developed by a British researcher, that calculates the days until bacteria growth speeds up, based on storage temperature:

D = 86.939 - 4.109T + 0.048T² (where D is the days until rapid bacterial growth and T is the storage temperature in degrees Celsius).

Adding a standard 7 days of refrigerated storage to this number gives a good estimate of how long eggs remain safe. For example, if eggs are kept at 28°C, they last about 16 days, but if stored at 10°C, they can stay good for as long as 57 days. Usually, egg producers set the best before date conservatively to around two weeks, because fridge temperature and handling can vary throughout the year.

When eggs arrive at supermarkets, they can be very fresh — sometimes laid in the morning and on store shelves by the evening. Naturally, you might want to pick the freshest eggs to get that great taste and nutrition, but unfortunately, it's hard to tell just by looking or holding them. The only sure way to check freshness is by cracking one open. Fresh eggs have a cloudy white due to dissolved carbon dioxide, and the thicker the firm part of the egg white around the yolk, the fresher the egg.

Interestingly, very fresh eggs aren't ideal for boiling because their internal gases cause the shell to stick tightly, making peeling difficult. It’s better to use eggs that have been stored for a few days for easier peeling.

To extend the life of your eggs, store them in the main fridge compartment rather than the door where temperatures fluctuate more. Keep them in their original carton with the pointed end down, which helps maintain freshness by keeping the yolk centered and the air cell stable. Avoid transferring eggs to special egg holders if possible, as the carton offers better protection and less contamination risk.

When refrigerated properly, eggs can stay good for 3 to 5 weeks beyond the best before date. So even if the printed date has passed, as long as the eggs don’t show signs of spoilage, you likely can still use them.

If you are unsure about whether an egg is still good, your senses are a big help. A rotten egg typically produces a very strong, unpleasant sulfur smell that is unmistakable. If you smell anything like that, don’t try to eat the egg—it’s best to throw it away immediately. Never hesitate to discard eggs with bad odors, even if the date says it should be fine.

Some common myths about testing egg freshness—such as seeing if eggs float in water or inspecting for water droplets—aren’t always reliable. The best approach is to break the egg open and check the inside for any unusual appearance or smell before deciding to use it. If you find any signs of spoilage, discard the egg without hesitation.

If you notice the eggshell has cracked before use, it’s important to be extra cautious. The eggshell naturally resists bacteria thanks to an antibacterial enzyme in the egg white called lysozyme, but a crack exposes the inside to harmful bacteria. For cracked eggs, make sure to cook them thoroughly and consume on the same day to minimize any risk.

Once eggs are cooked—whether as fried eggs, omelettes, or boiled eggs—their shelf life shortens significantly. Cooked eggs stored in the fridge should be eaten within 2 to 3 days to ensure safety and freshness, while boiled eggs with shells on last about 3 days refrigerated. Peeled or cracked boiled eggs should ideally be eaten within a day.