How to tell if an egg is bad

Keep eggs cold and cook them until firm, because no kitchen test can show that an egg is free of Salmonella.

Hands cracking an egg into a small separate bowl on a kitchen counter to check it before adding it to the rest — Photo: Quang Vuong / Pexels

Area: KitchenFrom age 12Time to learn: 10 minutes

Store eggs at 40°F (4°C) or below, read the carton date, crack each egg into a separate bowl to check for a bad smell, and treat the egg float test as a sign of age, not of safety.

SafetyNo home test detects Salmonella. Older adults, pregnant people, children under 5 and people with weakened immune systems are at higher risk of food poisoning: serve them eggs only when fully cooked. For any recipe that calls for raw or undercooked egg, use pasteurized eggs, which USDA says may be used safely without cooking. A food handler certificate course covers egg handling and cooking temperatures in more depth.

Why it matters

An egg can go wrong in two ways: it can spoil, which you can usually smell, or it can carry Salmonella, which you cannot see, smell or float-test. USDA notes that clean, uncracked, fresh eggs can still contain Salmonella Enteritidis, so cold storage and thorough cooking do the real safety work. The float test shows only that the air cell inside the shell has grown, which happens as any egg ages.

CDC estimates that Salmonella bacteria cause about 1.35 million infections in the United States every year, most of them from contaminated food.

Source: Centers for Disease Control and Prevention, About Salmonella Infection, 2024.Measured

How to do it

At the store, take eggs from the refrigerated case and open the carton. Choose clean shells with no cracks. Bacteria can enter through a crack, so never buy cracked eggs.
At home, refrigerate them right away at 40°F (4°C) or below. Keep them in their carton on a shelf in the coldest part of the fridge, not in the door. Eggs do need to be refrigerated: in the US, USDA-graded eggs are washed and sanitized at the plant, and shell eggs packed for consumers must be labeled Keep Refrigerated. Health Canada also lists eggs in the shell as a refrigerator food.
Never leave refrigerated eggs out for more than 2 hours. A cold egg left at room temperature can sweat, which helps bacteria move inside. Do not wash eggs at home: the wash water can be drawn in through the pores in the shell.
Read the carton. On USDA-graded eggs, an EXP or Sell By date can be no more than 30 days after packing, and a Use By or Best Before date no more than 45 days including the packing day. How long eggs last in the fridge: USDA gives 3 to 5 weeks for raw eggs in the shell, Health Canada gives 3 to 4 weeks, and FDA advises using them within 3 weeks for best quality.
If you use the egg float test, lower the egg into a bowl of cold water. If it floats, its air cell has grown large enough to keep it buoyant: the egg is old and lower in quality, but USDA says it may still be safe to use. If it sinks, its air cell is still small. Neither result tells you whether it carries Salmonella.
Crack each egg into a small, separate bowl before adding it to anything else. Look at it and smell it. A spoiled egg has an unpleasant odor, raw or cooked. Discard any egg with an off odor or an unusual appearance.
Cook eggs until both the yolk and the white are firm. Cook casseroles and other dishes containing eggs to 160°F (71°C) on a food thermometer; Health Canada sets 165°F (74°C) for egg dishes. Reheat leftover egg dishes to 165°F (74°C).
Refrigerate hard-boiled eggs within 2 hours of cooking and eat them within 1 week. Cooked egg dishes keep 3 to 4 days in the fridge.

Common mistakes

Treating an egg that sinks as safe. The float test measures age, and Salmonella can be inside a fresh egg that sinks.
Throwing out a floating egg without checking it. An old egg may still be safe; crack it into a bowl and smell it first.
Storing eggs in the fridge door. USDA advises keeping them in their carton in the coldest part of the refrigerator.
Washing eggs before storing them, which can pull bacteria through the shell.

You can do this when …you can store a carton correctly, read its date, crack an egg into a separate bowl and judge it, and explain why an egg that sinks can still make someone sick.