How to Cure Sour Crop in Chickens (Is It Contagious?)

It’s a yeast overgrowth in a pouch that should have moved its contents down to the gizzard hours ago. Left alone it gets worse, not better, and the birds that die from it die of malnutrition and dehydration, not the yeast itself. Caught early, most hens recover.

What the crop is
What sour crop is
What causes it
What it looks and smells like
Is sour crop contagious?
How to treat it
Keeping it from coming back
When to call a vet

What the crop is

The crop isn’t a stomach and it isn’t part of digestion in the way you’d think of it. It’s a soft, expandable pouch off the esophagus, low on the right side of a chicken’s breast, and its job is to hold what your hen eats until her gizzard is ready to grind it. On a good day it fills through the afternoon, hangs full and warm at roost, and empties overnight while she sleeps. By the time you’re out with the feed in the morning it should be flat to the touch.

A normal crop holds roughly an ounce and a half of feed — about the volume of a shot glass, or one loose handful of pellets. It’s lined with the ordinary mixed flora of the gut — beneficial bacteria alongside small numbers of yeasts and molds that a healthy balance keeps in check.^[1][3]

Trouble starts when something knocks that balance sideways.

What sour crop is

Sour crop is Candida albicans — the same opportunistic yeast that causes thrush in babies and vaginal yeast infections in adults — proliferating out of control inside the crop, the muscular pouch at the base of her neck where feed collects before it moves on to her stomach.^[1][2] Candida lives in a chicken’s gut in small numbers as a matter of course; it’s a normal commensal until the conditions in the crop stop keeping it in check.^[1]

What stops keeping it in check is usually a slowed or stalled crop. When food sits too long, fermentation shifts the acidity, the beneficial bacteria fall off, and the yeast has room to bloom. From the outside you smell the fermentation before you see anything else. From the inside, a heavy overgrowth thickens the crop lining with a whitish pseudomembrane that you may be able to see if you look inside her mouth.^[1][2][3]

What causes it

Anything that slows the crop down, disturbs the flora, or hands the yeast an advantage.^[1][2][3]

A recent course of antibiotics. The most common trigger by a distance. Broad-spectrum antibiotics kill the beneficial gut bacteria along with whatever they were prescribed for; the yeast, unbothered, moves into the empty space.^[1][2]
Dirty water and moldy feed. Fermenting feed and biofilm-slimed waterers are a constant low-dose challenge that a well-flora’d bird handles fine, until she doesn’t.^[1][3]
A vitamin A shortfall. Chronic and easy to miss in a flock scraping for supplemental greens through winter. Vitamin A deficiency is a documented risk factor for candidiasis in poultry.^[1]
An impacted or slow-emptying crop. Long tough grass, a piece of bedding she swallowed, a mass at the outlet. The crop can’t push what’s in it down, everything ferments, and the yeast follows.^[3]
A heavy worm load. Systemic; pulls the whole bird down at once.

Chicks and juveniles are the most susceptible, because their gut flora hasn’t fully established.^[1]

What it looks and smells like

In more advanced cases there’s a thin clear-to-yellow discharge running out of the corner of her beak, and if you look inside her mouth you may see whitish plaques on the tongue or the roof of the mouth.^[1][2]

The birds you catch late have usually been off feed for a day or two and are losing weight. Watch for:

Fluffed feathers and standing apart from the flock
Loose or foul-smelling droppings
A drop in laying, or shells thin enough to break in the nest
Weakness in the legs, listlessness, an unwillingness to move

Is sour crop contagious?

Not in the way people usually mean. Sour crop isn’t a disease one bird catches from another; it’s a yeast overgrowth that starts inside a hen, driven by conditions in her own crop, not by contact with a sick flockmate.^[1]

The organism behind it, Candida albicans, lives quietly as normal flora in healthy poultry. It only becomes a problem when something disturbs the balance in one bird: a recent antibiotic course, a fouled waterer, a stretch of moldy feed, a heavy worm load, a vitamin A shortfall. Young chicks are the most susceptible.

That’s why you’ll sometimes see two or three hens go down with sour crop in the same week and worry the coop has an outbreak. It looks like something is spreading through the flock. What’s really happening is that the birds share the same risk factors, the same waterer, the same feeder, the same round of antibiotics after a respiratory scare. Fix the shared cause and you protect the whole flock; the prevention section below runs through the specifics.

What about people? Sour crop isn’t contagious to humans. Candida lives on us as normal flora too, and the authoritative avian-medicine references don’t describe candidiasis as something you catch from your chickens. Wash your hands after handling a sick bird and skip face-to-beak contact until she’s recovered. If you’re immunocompromised, or care for someone who is, wear gloves while you’re treating her and check in with your own physician.

How to treat it

The frame first. A diagnosed hen with sour crop needs three things: the crop cleared, the yeast knocked down, and the underlying cause fixed. Only the first is a home job in mild cases; the second is a vet’s job.

Home care sequence

Isolate her.

Move her to a clean brooder or a dog crate somewhere quiet, with a shallow water dish changed twice a day and a soft, easy feed like scrambled egg or wet mash once she’s willing to eat. She’s not going to be chased around a yard for treatment, and she’s not going to compete for the waterer in her state.
Massage the crop, gently, a few times a day.

Cupped hand, palm warm, slow downward strokes with light pressure toward her keel. You’re helping the crop’s own muscle move contents on, not squeezing anything out. Aggressive kneading of a fluid-filled crop pushes contents up toward the airway.^[3]
An Epsom flush, once, first thing in the morning.

On an empty crop, one teaspoon of Epsom salts dissolved in an ounce of warm water, given slowly by dropper into the side of her beak.^[3] It works osmotically to move stuck contents through. It’s a single flush, not a two- or three-day protocol; extended dosing is dehydrating for a bird already dropping weight.

Skip these — they don’t work or they hurt her

Do not hold her upside down to make her vomit.

It’s a widely repeated technique in owner forums and it’s one of the fastest ways to give a weak hen aspiration pneumonia — sour crop fluid inhaled into her airway seeds a lung infection in hours, and once a bird’s lungs are wet with stomach contents the recovery rate falls off a cliff.^[3] If the crop is severely distended, or the bird is too weak to hold her head up, a vet needs to drain and flush it under sedation.^[2] That is not a home procedure.
Skip the molasses and the tomato juice.

Both circulate in forum advice and neither has support in the veterinary literature. If the underlying issue is a hard impaction rather than a yeast overgrowth, an osmotic laxative won’t clear the obstruction and can make her worse.
Copper sulfate is vet-directed only.

Copper sulfate at 1:2000 in the drinking water — roughly half a gram of copper sulfate crystals per liter of water, or about two level teaspoons stirred into a five-gallon bucket — is a documented historical treatment for candidiasis in poultry, and it’s still on the University of Maryland’s crop-issues page.^[3] It is also toxic if the dilution is off. Modern practice reaches for nystatin, an oral antifungal — think of it as the veterinary version of the mouth-thrush drops a pediatrician prescribes for a baby — a vet can prescribe by mouth or mixed into feed, before it reaches for copper sulfate; fluconazole (the same drug adults get for stubborn yeast infections) is the pet-bird equivalent.^[1][2] A full antifungal course is a phone call to a vet, not a jar off the shelf.

If she’s cleared her crop within a day or two of the flush, is eating again, and the smell is gone, she’s out the other side. Watch her for a week. If she stalls, or the smell comes back after eating, she’s onto the antifungal course, and she needs a vet to prescribe it.

Keeping it from coming back

Prevention is a boring answer and it’s the right one. Clean water, dry feed, no long antibiotic courses without a probiotic tail, and a well-fed bird.^[1][3]

Scrub waterers weekly, more often in heat. Biofilm and slime feed the low-grade challenges that push a bird over the edge.
Store feed dry, and toss any that smells off. Fermenting feed is one of the fastest routes into a whole-coop event.
After any antibiotic course, offer a probiotic. Powder in the feed or a live-culture yogurt does the job. You’re repopulating the beneficial flora before the yeast finds room.^[1]
Watch for vitamin A shortfalls in winter. Layer pellet is fortified for it; scratch grains aren’t. If your flock is on scratch and yard forage through cold months, a leafy green rotation matters.
Apple cider vinegar in the water once a week. Widely used in backyard flocks, no controlled evidence to point to, and probably not harmful. Cheap enough to keep in the routine if you want it; not a substitute for anything above.

When to call a vet

Now, if any of this is happening:

She’s off her feet, or on her keel breathing hard
You can see white plaques through her open beak, or she’s not swallowing at all
You’ve done the Epsom flush and her crop is still full and warm 24 hours later
She’s dropping visible weight or her eyes are dulling
More than one bird in the flock is showing signs and you can’t isolate the shared trigger

Sour crop caught early is a low-drama fix. Sour crop ignored for a week is a bird you’re at risk of losing. If your local search is coming up empty for an avian or poultry vet (which it often does), Vet Corner covers how to find an avian vet and when a televet is enough. A televet can review a photo of her mouth, prescribe nystatin if that’s what she needs, and tell you within a few minutes whether this is still a home call or one for hands rather than a webcam.