What Causes Deformed Chicken Eggs and Other Egg Abnormalities?

When You're Raising Laying Hens, You May See Some Strange Eggs Like These

What Causes Deformed Chicken Eggs and Other Egg Abnormalities?

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Egg abnormalities and deformed chicken eggs occur with almost every breed of hen at some point in her egg laying career. Eggs laid by non-commercially bred hens vary considerably in size, shape, and color. People who have a small flock of backyard chickens with several different chicken breeds can learn to recognize eggs from each hen. It’s easier for them to know who’s laying and who isn’t, how often and when, and which hen may be having health issues because of consistent abnormalities. For people like me who have a larger flock,  it’s harder to tell and requires us to separate a suspected hen to determine her laying quality and quantity.

The Anatomy Of Egg Laying

If you butcher your own birds and any of them are of egg laying age (5 to 7 months for most all breeds), you’ll see the eggs waiting inside her. There’ll be a cluster of little tiny yellow specks that look like grains of sand with small pebble like ones around them, graduating in size, larger and larger. These are the yolks. Have you ever wondered how do chickens lay eggs? When the yolk for the day is ready, it enters the oviduct where it can be fertilized.

Next, the egg white is added, then it receives two membranes that help to keep the nutrients in and to keep its shape. Finally, the shell is put on and the egg moves to just inside her vent. The whole process takes about 24 hours. Now, she’s ready to lay! Boy will she let you know when she’s done it. My whole flock gets excited and cackles for each and every egg, every day. You would think they would be used to doing it and not put on such a show, but it’s a production of cackles and crows for every egg! This is a very basic and simple explanation of the egg production process and somewhere in this straightforward, yet complex process, things happen that cause deformed chicken eggs and egg abnormalities.

Just in way of a reminder, a pullet (a hen under a year old) will lay smaller eggs than she will as she grows and matures into a hen. Of course, age is the first thing that comes to mind since most chicken breeds begin laying between 5 to 6 months of age. As a hen matures, the size of her eggs and the frequency of her laying will increase. Once she begins laying, it usually takes her 7 to 10 weeks to work up to full production. Depending on the breed and the lifestyle of your hen, you can expect her to lay for up to 10 years. The average lifespan of a hen is 14 years. If your main goal is egg production, then you probably wouldn’t want to keep your hen past 3 to 4 years of age as this is the age range she will be most productive. When I have a hen who is unproductive for more than four months out of the year, I cull her. That is of course unless she is special.  

Deformed Eggs

Who’s Laying And Who’s Not

Judging which hen is laying and which isn’t is not an exact science, but there are some signs. Before a hen begins to lay, you will see a yellow color around her vent, eyes and earlobes. After she has been laying for a few months, the yellow in these and her beak will fade slightly. After about six months of laying eggs, her feet, toes, claws and shanks will also fade. When she quits laying, you will see the color come back to these. This is kind of interesting to me since the bright color of her cone and wattles is a surefire sign that she is laying or about to. When she stops laying she will turn pale pink. It seems just the opposite from her other body parts.

Deformed Chicken Eggs and Egg Abnormalities

The most bizarre of the deformed chicken eggs that I’ve ever found in my flock is the shell-less egg. It doesn’t happen often, but every once in a while, I get a chicken laying soft eggs. As you can see in the photo, it’s perfectly formed down to the protective membrane, but the shell simply didn’t form around the egg. If you reach into the nest for your eggs without looking, it’s a pretty freaky feeling to grab hold of one of these. These types of deformed chicken eggs usually happen in a chicken that is just beginning to lay. I have only had this happen four or five times in all my years of owning chickens.

If you have more than one of these deformed chicken eggs, or find them frequently, be sure you your chicken feed offers a balanced diet and add calcium. Be sure to not eat this egg. You can give it to your dogs or hogs, but not to humans. Since the protective shell didn’t form, it’s very probable that bacteria has gotten through the membrane contaminating the egg.


Another big abnormality is the double yolk eggs. I have to say in my 30-plus years of chicken keeping, I’ve had less than 10 of these. These don’t really count as deformed chicken eggs. This photo was taken a long time ago. I remember taking it because it was the first one I had received from my girls in years and I didn’t know when I would have another one. The double yolked egg is just an egg that has developed two yolks. Kinda like it wanted to be twins! This egg is perfectly safe to eat.


Your eggs may be weirdly shaped. You may have an outcropping on your eggshell. This is just a little extra deposit of calcium like you can see in this photo. Interesting “swirlies” often form in the shell making process.



Even though I’ve never had one, I’ve heard of having an egg inside an egg. This is caused when an egg gets backed up for some reason and goes through the last production stages twice.

I had this egg from one of my younger hens. It was such a puzzle to me. The egg is cracked almost all the way around, yet the protective coating (called the bloom) sealed the egg.


Not a true abnormality, but worth noting, is blood around the yoke. It’s considered a hereditary characteristic in some chicken breeds. Blood in chicken eggs isn’t an indication of fertilization. This kind of egg is completely edible. If you have a rooster, you may notice a white or slightly discolored spec in your yolk when you crack your egg. Congratulations! You have a fertile egg and given the right opportunity it would’ve become a chick. This egg is edible, which is a good thing because almost all my eggs are fertile. Yep, my guys are on the job. As you can see in this photo, this was the shell-less egg. I cooked it for the dogs.


Of course, if you crack an egg and it smells funny, don’t eat it! It’s good to know how to perform an egg freshness test when in doubt. One of my grossest memories is when I was helping my grandmother, and I use the term “helping” loosely, fix breakfast. She had fried the bacon, which came from their smokehouse and was cooking eggs. She had fried two or three and reached for another. When she cracked it open and plopped it into the hot skillet, there was a half-developed baby chick! Oh boy did it stink! Needless to say, she rushed it out the back door then cleaned the skillet. I remember she said, “That’s what I get for not cracking it into a bowl first.”  She had to explain to me that she had found a nest of eggs and thought she had tested them all for freshness, but that when you’re not sure, you should crack the egg into a bowl first and then use it. She couldn’t have taught me a more memorable lesson. As you can imagine, neither one of us had eggs for breakfast.

What is the most abnormal egg you’ve had in your flock? Have you experienced any of these? I really enjoy that no two eggs are exactly the same. I can tell which breed laid which egg, but not which hen. Can you tell?

Originally published in 2015 and regularly vetted for accuracy.

10 thoughts on “What Causes Deformed Chicken Eggs and Other Egg Abnormalities?”
  1. It seems all our eggs, from 7 different hens, have insufficient whites. When you boil them and then peel the eggs there is always a gap between the egg and the shell at one end. Makes it hard to make deviled eggs because the white doesn’t completely enclose the yolk.

    Is there something missing in their diet or what causes this.

    1. This is the exact thing that I am experiencing from the eggs that I bought so I thought, it was injected to look bigger, hence I came online to feed my curiosity

  2. The air sack space should not be a problem. A cooking magazine told me to gently roll the eggs back and forth during the first couple of minutes of hard boiling to distribute the white more evenly. I hope it works for you because when I take the time to perform this extra step of rolling the eggs over, it works for me.

  3. I have at least one hen ( a small flock of mostly California Sexlings), who has been laying for 3-4 months. She is consistently laying an egg that is flattened on one or more sides. The shell is still hard but is a little bit more pale than the other eggs from hens of her same breed. The white and yolk looks and smells and tastes normal, but I’m wondering what I can do to help her lay a correctly shaped egg. I’m not sure which one of my 19 chickens it is, either. Whatever help you can offer would be greatly appreciated. I’m a new flock owner.

    1. Hi Debra, this could be caused by several things. If your hen is stressed, the egg doesn’t spin correctly in the oviduct, which can cause wavy, creased, or otherwise misshapen eggs. Also, if she had infectious bronchitis at some point in her life, it can affect the shell gland for a while, usually about six months, which also keeps the eggs from correctly spinning during formation. There’s nothing you can do about infectious bronchitis other than keeping your hens comfortable and waiting for them to recover. Whether the flattened side is caused by IB or stress, my best advice is to take a look at your coop and run to be sure it provides what your hens need to be happy. Here is another amazing article on those weird eggs: https://backyardpoultry.iamcountryside.com/eggs-meat/why-hens-lay-weird-eggs/ and this one talks about the five basic needs for happy hens: https://backyardpoultry.iamcountryside.com/chickens-101/chicken-husbandry-five-welfare-needs/. Good luck!

  4. We got a tiny egg from a 3 year old chicken with no yolk! We also got an egg with thick swirled ridges. Trying to figure out if my hen is okay?
    Of course we’ve also had the double yolk eggs a few times and the eggs with warts.

  5. I have one hen in a group of four when she first started laying it was huge and always a double yolk. She never evolved to laying every day like the others but usually only missed one day every couple. Now after having them a yr. She no longer lays doubles and her she’ll is wavy or indented as if it got stuck coming out with a ring indent eggs still lg.

  6. I have a hen that occasionally lays an egg that looks like a bowling pen, is she stressed? I had moved them to a different place but I let them out to forage almost daily. The 3 hens I have usually lay 3 to 4 eggs daily, I feed them kale, Romaine lettuce, fruit like grapes, blueberry and watermelon but they really love cucumbers. Are they considered stressed when they lay the odd shaped eggs? They do this odd shape egg very seldom.

  7. Thanks for this article, am a new starter in backyard poultry with just 90 Layers I’ve gotten one soft shell egg within the first four months of laying. I was wondering what could cause this. You mentioned a chick can lay eggs for up to three years but I was told that i should sell off my chicks after a year laying period as they may be less productive. Can this be true?

  8. I have a hen laying soft shelled eggs which are mostly broken. The hen is not eating the egg. I have put oyster shell, grit and other tonics etc to try to improve the situation. I think I have identified which hen is so unfortunate as she has a soiled vent area. I don’t know what else to do. She seems lively and interested otherwise and is eating Her comb is pale pink and her feathers are ruffled but she may be moulting. Any ideas welcome.

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