In case you haven’t heard the news, egg prices are at an all-time high. Americans are scrambling to get their hands on a discount dozen—I, for one, have been paying specialty market prices at my local Stop & Shop. In times like these, we make sacrifices. Maybe you’ve stopped buying organic, settled for grade A instead of AA, or you’re buying your eggs in bulk. If you are stocking up on Costco-sized cartons, though, there’s something you should consider: How long do you have before those eggs go bad? 

We worry about the expiration date of meat or fish, but what about other less obviously potent products? Can eggs go bad, just like those week-old chicken thighs giving your fridge an unsavory stink? The short answer: yes, eggs can go bad, but there are a few different ways for this to happen—some more dangerous than others. 

How to tell if eggs are bad or good:

When we talk about an egg going bad, there are a few different things we might mean: 1) The egg can be compromised in quality—i.e. it won’t taste very good—but won’t pose a significant health threat. 2) The egg can be contaminated with salmonella, a pathogenic bacteria, which could lead to severe sickness if consumed. Let’s break down the ways an egg might be contaminated, and how to know if it’s okay to eat.

Spoilage

Over time, foods that have been sitting in your fridge can go bad without necessarily posing a health threat. “The classic example for this is spoiled milk,” explains Dr. Don Schaffner, Extension Specialist in Food Science, Distinguished Professor at Rutgers University, and co-host of the Food Safety Talk podcast. “Milk is not going to be unsafe if it has been pasteurized. But milk that’s been hanging out in the fridge for long enough will eventually not smell good, not taste good, and not look good. The same applies to eggs.”

So how can you tell if an egg has gone bad? You may have heard of a method called the float test or the water test, which involves placing an egg in a bowl of water and seeing if it sinks (meaning it’s good to use) or floats (no good). The theory is that, as an egg ages, the air pocket inside it grows larger, buoying an old egg to the surface. But, according to Dr. Schaffner, “there is no scientific basis for the egg float test.” So experimenting to see if your egg sinks or swims is not a reliable way to measure its quality.

The best way to tell if an egg is bad, he says, is to trust your senses. “If the egg looks or smells different than how eggs usually look or smell to you, that would be an indication that maybe some spoilage bacteria got in there,” advises Dr. Schaffner. 

Maybe the egg is emitting a sulfurous smell or otherwise unpleasant odor—eggs can absorb smells from the inside of the fridge, so if you store it next to a fish fillet, the egg will eventually start to smell fishy. That egg’s not going to taste good and should be discarded.