Why Do Chickens Lay Soft Shell Eggs? Causes, Fixes and Prevention
 

Soft Shell Eggs: What’s Going On?

If you’ve been keeping chickens for a while, chances are you’ve come across a strange, floppy egg with no shell to speak of. Sometimes it’s a one-off blip in the system. But when your hens keep laying weak or rubbery shells, it’s not just odd—it’s a flashing warning light that something’s off with nutrition, health, or management.

A proper shell isn’t just for looks. It’s a hen’s first line of defence against bacteria sneaking in. Without it, both the egg and the hen are at risk. Soft-shelled eggs form when the membranes are intact but the calcium carbonate shell is missing. Thin shells have some calcium, but not enough to do the job. And those rubbery “balloon eggs”? They’re just another variation of the same problem.
 

How Hens Actually Make an Egg

Inside every hen is an incredible production line that churns out an egg in just 24–26 hours. It all starts in the ovary, where a yolk forms. Once ready, the yolk drops into the infundibulum—a funnel-shaped section of the oviduct. If a rooster’s been busy, fertilisation happens here. The yolk only lingers 15 minutes before moving on.

Next comes the magnum, where the egg white (albumen) gets layered on over about three hours. After that, the yolk and whites move into the isthmus, where the inner and outer membranes form—those layers you see when you peel a boiled egg.

Then comes the uterus (aka the shell gland). This is where things get serious. Over the next 20 hours, calcium carbonate is pumped in to form the hard shell. One single egg drains 1.7–2.4 grams of calcium—roughly 10% of a hen’s total body reserves. She draws this from both her diet and her medullary bone, which acts like an emergency calcium bank. Bicarbonate ions and a protein scaffold lock the shell into place. Finally, a waxy coating called the cuticle/bloom seals it off before it exits through the cloaca.

                                            

That whole process is finely tuned. Knock it out of balance—through poor diet, hot weather, stress, or disease—and you’ll start seeing soft, thin, or misshapen shells.
 

Why Shells Go Wrong

Nutrition: not just about calcium

Calcium is the star, but it’s useless without its sidekicks. Vitamin D3 is what helps hens absorb calcium from the gut, and phosphorus is what locks it into bone and shell. Too much calcium without enough phosphorus? That can backfire—excess calcium gets dumped, while phosphorus runs short. Protein is another player. Too little and hens can’t build the protein matrix of the shell. Too much and it throws off metabolism, leaving the shells just as weak.

Age and genetics: young, old, and overworked hens

Pullets (young hens) often lay a few softies when they’re just getting started. Usually nothing to worry about—it fixes itself. Older hens, on the other hand, don’t absorb calcium as well and lay bigger eggs that spread what calcium they do have more thinly. High-production hybrids like ISA Browns/Hy-Lines/Lohmanns are particularly vulnerable—they’ve been bred to lay like machines, which puts their bodies under constant strain. Add molting into the mix, where nutrients get diverted to feather regrowth, and shell quality takes another hit.

Stress: the silent saboteur

Heat stress is brutal for eggshells. When hens pant to cool off, they lose carbon dioxide. That shifts blood chemistry, cutting down on the bicarbonate needed for shell formation. Appetite also drops in hot weather, meaning less feed—and less calcium—goes in. Other stressors—predators lurking, overcrowding, bullying, or sudden loud noises—can throw off the oviduct’s timing. Eggs get laid too early, before the shell is finished. Poor ventilation and ammonia build-up in the coop are also calcium blockers.

Health problems: from viruses to broken eggs inside

Some diseases hit shell quality hard. Infectious Bronchitis and Egg Drop Syndrome damage the oviduct, leaving hens producing wrinkled, thin, or shell-less eggs. Salpingitis (inflammation of the oviduct) can cause deformed or pus-filled eggs.

There’s another danger too: soft shells can collapse inside the hen as she lays. If that happens, you might see egg white or yolk leaking from the cloaca. A broken egg internally can quickly turn into a life-threatening infection. It’s not something you can manage at home—your hen needs a vet, and fast. Without antibiotics and proper care, this situation is often fatal.

Parasites also play a role by stealing nutrients, leaving less available for shell production. And any illness that diverts energy away from reproduction shows up in shell quality.
 

How to Fix Soft Shell Egg Problems

The good news? Most cases can be prevented—or fixed—with good feed, proper management, and close observation.

Fixing Soft-Shell Egg Problems

1. Nutrition First

• Feed a complete layer ration with 16–18% protein and 3–4% calcium.
• Offer free-choice calcium like oyster shell, shell grit, or baked eggshells. Larger particles (>2 mm) stay in the gizzard longer and drip-feed calcium overnight.
• Timing: Give extra calcium in the afternoon when hens stock up for night-time shell building.
• Keep treats and scraps to under 10% of the diet. They dilute nutrition fast.
• Ensure vitamin D3 is present and keep calcium-to-phosphorus at 6–8:1.
 

2. Environment & Flock Management

• Keep coops cool and well-ventilated. Fresh water is a must, and electrolytes help in heatwaves.
• Feed in the cooler parts of the day during summer.
• Provide enough space and calm to stop bullying and stress.
• Maintain a clean coop to avoid ammonia build-up.
 

3. Health Checks

• Call a vet if soft shells persist and hens look off-colour.
• Rule out parasites and check for diseases like Infectious Bronchitis or Egg Drop Syndrome.
 

Quick Reference: Common Problems & Fixes

• Young pullet → Give her time; keep her on layer pellets.
• Older hen → Offer free-choice calcium; try a senior layer feed.
• Heatwave → Ventilate, add electrolytes to water, feed in cooler hours.
• Too many treats → Cut back to 10% of diet max.
• Molting → Up the protein and calcium—feathers steal resources.
• Stress or scares → Predator-proof, stop overcrowding, keep things calm.
• Persistent soft shells plus sickness → Straight to the vet.
 

Final Thoughts

Soft-shelled eggs aren’t just weird—they’re the canary in the coal mine for your flock’s health. Sometimes it’s a harmless blip (like a pullet finding her rhythm), but it can also point to serious problems with feed, stress, or disease. And because producing an egg pulls huge amounts of calcium, protein, and energy from the hen every single day, it doesn’t take much to throw the system out.

Prevention is easier than cure. Feed properly, manage the coop, reduce stress, and keep a sharp eye on your birds. Most problems are fixable once you know the cause. And the reward? Strong, crackable shells and a healthier, happier flock.
 

Soft Shell Eggs FAQs 

1. Why do chickens lay soft shell eggs?
Chickens lay soft shell eggs when they can’t deposit enough calcium carbonate during shell formation. Causes include diet, heat stress, age, or disease.

2. How do you fix soft shell eggs in chickens?
Give a balanced layer feed, free-choice calcium, adequate vitamin D3, and manage stress. Vet care may be needed if it persists.

3. Can heat stress cause soft shell eggs?
Yes. Panting lowers bicarbonate levels needed for shells and hens eat less in hot weather, reducing calcium intake.

4. Do pullets lay soft shell eggs?
Yes. Young hens often lay soft or thin shells while their systems adjust. It usually resolves in weeks.

5. Why do older hens lay thin shells?
Older hens don’t absorb calcium as efficiently and their bigger eggs spread what calcium they do have too thin.

6. What diseases cause soft shell eggs?
Infectious Bronchitis, Egg Drop Syndrome, and Salpingitis can all disrupt shell formation in laying hens.

7. Can too many treats cause soft shells?
Yes. Excess scraps dilute the nutrition from layer feed, reducing calcium and protein intake.

8. What supplements prevent soft shells?
Oyster shell, grit, or baked eggshells for calcium; vitamin D3 to help hens absorb it.

9. How does stress affect eggshells?
Predators, overcrowding, or loud noises can mess with the oviduct’s timing, so eggs get laid before the shell is finished.

10. Can a soft shell egg break inside a hen?
Yes. If it collapses in the cloaca, you may see yolk or white leaking. It’s dangerous, often fatal, and needs urgent vet care.