Why Do My Chicken Eggs Smell Bad? [How To Tell If They’re Bad]

It’s fair to say that most of us have smelled a rotten egg before. You crack it open into the frying pan, and a horrible smell drifts up. It almost smells like sulfur or, worse, a skunk.

However, some eggs can smell somewhat fishy when still intact. Have you ever wondered why? 

Why do my chicken eggs smell bad? How do I know if they are still good?

Chicken eggs can smell bad due to a mix of genetics and nutrition in your chicken. Most commonly, the smell is due to an overabundance of canola meal in your hen’s diet.

In this article, I will go over why your eggs smell and what steps you can take to keep this from happening. I will also explain how to tell if your eggs are still safe to eat.

Why Do My Chicken’s Eggs Smell Bad?

Most of us associate smelly eggs with ones that are rotten and unsafe for consumption. But if you are an avid chicken farmer, like me, you may have noticed that your eggs have a fishy smell.

You may even notice this if you buy low-quality store-bought eggs.


Some eggs have a fishy smell because of trimethylamine or TMA, which is a by-product of the normal digestion process in hens. 

Choline begins to ferment in a chicken’s digestive tract, along with the next digestion step, which is the culprit. This is how TMA is made into TMAO, or N-oxide, which is triethylamine free from odor.

However, this process sometimes doesn’t go as planned, and it mostly comes down to the hen’s diet.

Often, due to a hen’s dietary intake, there is an increase of TMA in their digestive system. When this happens, her gut is unable to process it into TMAO. This results in excess TMA that builds up in the egg yolk, resulting in that fishy smell. 

The chicken may also have a gene mutation that makes it difficult for her to turn TMA into TMAO. Chickens who lay brown shells are most susceptible to this mutation. 

In most cases, eggs that smell of fish are a result of canola meal in their diet. 

What is Canola Meal?

Canola is a rapeseed plant with an oil low in glucosinolates, which are natural components of more pungent plants. Oils low in glucosinolates produce a meal that is low in erucic acid.

Canola meal is the by-product of extracting the oil, and it is commonly found in chicken feed.

Is Canola meal Dangerous?

In large quantities, it can be. However, in some feeds with as few as 3% being canola meal, this can lead to foul-smelling eggs, especially in hens who lay brown eggs. 

A higher rate of canola meal has led to goiters and other thyroid-related issues in chickens. 

But most chicken food is well balanced to prevent eggs that smell fishy and any long-term effects from canola meal. 

How Do I Keep My Eggs From Smelling Fishy?

Know what you are feeding your girls. While canola is often used as a small extra boost of omega 3, it seems to be problematic in excess. 

By paying close attention to the list of ingredients in your chicken’s feed, you can tell if the canola meal is being used as an additive or an ingredient. 

The difference between the two is that an additive is only a small amount, while an ingredient makes up for a substantial amount of the food.

Also, read the ingredients on any treats you are giving your hens. For example, many are treated with canola, so you will want to keep those to a minimum. 

One treat that does not contain canola is sunflower seeds.

And just know that any hens in your flock that lay brown eggs have a better chance of being affected by the TMA by-product during digestion.

Is it Okay to Eat Eggs That Smell Like Fish?

Though they may have a funny and unpleasant taste, eating fishy-smelling eggs is perfectly safe.

How Do I Know if My Eggs are Bad?

As mentioned at the beginning of this article, no one wants to eat a rotten egg. However, what usually happens is that the quality of the egg begins to decline as the air pocket inside gets bigger, which causes the egg white to thin out.

But only when an egg begins to rot because of bacteria or mold is it truly bad.

However, we should all be aware of ways to determine whether or not our eggs are safe to eat. So let’s look at some of the tried and true methods.

  • Check the date
  • Closely inspect them
  • Use the sniff test
  • Do the float test

Check the Date

While this seems like the obvious way to find out if your eggs are safe, there is a little more to it. Often eggs are still perfectly fine past the expiration date.

In the United States, most egg manufacturers will label egg cartons with a sell-by date to let you know if your eggs are still fresh. But the sell-by date only means that the store should no longer sell eggs past that date, which is no more than 30 days past packing. 

This doesn’t necessarily mean the eggs have gone bad.

Closely Inspect Them

Believe it or not, a good visual inspection can tell you a lot about an egg’s freshness. 

The eggshell should not be cracked or covered with a powdery or slimy substance. These can indicate the presence of mold or bacteria. 

When you crack the egg into a bowl, look for any discoloration in the yolk, which can also indicate bacteria. 

If the egg whites or the yolk are runny, it could mean the quality of the egg has declined.

Use the Sniff Test

This method is the oldest and most reliable way of knowing if your egg is still good. All it takes is a simple sniff. Once you crack that egg, you will notice right away if the egg is rotten by the pungent smell. 

But if you sniff an egg, even one past its expiration date, and there is no unpleasant odor, chances are, it’s perfectly fine.

Do the Float Test

This is the method I use and is by far the most popular one to tell whether an egg is safe to eat. 

Simply fill a bowl or tall glass with water and gently drop your egg into the water. If the egg sinks, it’s still fresh and safe to eat. However, if the egg tilts upward and floats, it is usually no good. 

The float test works here because when an egg begins to age, small air pockets inside it grow larger. If the air pockets become big enough, the egg will float, letting you know it’s unsafe to eat. 


If your eggs have a fishy odor, it is likely due to your hen’s diet. But in most cases, it is perfectly safe to eat. 

However, this is different from eggs that have truly gone rotten. By using the simple methods in this article, you can determine if your eggs are still safe to eat. 

Related Articles