Spotting illness in chickens is one of those skills that develops over time. New keepers tend to either panic at every minor irregularity or miss serious problems until they’ve progressed too far for easy treatment. The middle ground — recognizing what’s normal, what’s concerning, and what’s an emergency — comes from learning the patterns of common illnesses and what they actually look like in real birds.
The complication is that chickens hide illness instinctively. As prey animals, showing weakness attracts predators, so birds work hard to appear normal until they can’t anymore. By the time a chicken looks visibly sick, the underlying problem has often been developing for days or even weeks. Catching things earlier requires recognizing the subtle signs before they become obvious, and that means knowing what specific illnesses look like in their early stages.
This guide walks through ten of the most common health problems that show up in backyard flocks, what each one looks like, what causes it, and what to do about it. The goal isn’t to replace veterinary care for serious situations — it’s to help keepers recognize what they’re seeing and respond appropriately before problems become emergencies.
A Note Before the List
A few principles apply across most chicken illnesses and worth understanding before going through specific conditions.
Chickens that act sick are sick. The flock’s instinct to hide illness means a bird visibly looking unwell has usually been struggling for some time. “Off” behavior — sitting puffed up away from the flock, not eating, not drinking, lethargic posture — is a serious sign regardless of how mild it appears.
Isolation often helps both the sick bird and the flock. A separate space with food, water, warmth, and reduced stress lets sick birds recover while preventing disease spread. Quarantine doesn’t have to be elaborate — a dog crate in a garage or spare room works fine for short-term care.
Many chicken illnesses share early symptoms. A lethargic bird with puffed feathers might have a respiratory infection, internal parasites, a reproductive problem, or any of several other issues. The early generic symptoms become more specific as conditions progress, which is why early identification matters.
Veterinary care for chickens is variable in availability and cost. Some areas have avian or poultry vets who handle backyard birds routinely. Other areas have only large-animal vets who don’t see chickens. Knowing what’s available locally before an emergency happens matters more than people realize.
1. Respiratory Infections (Mycoplasma, Infectious Bronchitis, and Related)
Respiratory illness is probably the most common health issue in backyard flocks. The category includes several different specific conditions, but they often present similarly enough that the practical response is the same.
What to look for: Sneezing, coughing, wheezing, or rattling sounds. Discharge from the nose or eyes. Swollen face or sinuses. Foamy or bubbly eyes. Open-mouth breathing. Reduced appetite. Birds standing puffed up with closed eyes.
What causes it: Various pathogens including Mycoplasma gallisepticum, Infectious Bronchitis virus, and Infectious Coryza. Stress, cold damp weather, poor ventilation, and contact with infected birds all increase risk. Mycoplasma in particular can stay dormant in seemingly healthy birds and flare up during stress.
What to do: Isolate affected birds immediately. Improve coop ventilation and reduce humidity. Provide warmth and easy access to water and food. Treatment depends on the specific cause — Mycoplasma responds to certain antibiotics (Tylan, Baytril) that require veterinary prescription in most jurisdictions. Viral causes don’t respond to antibiotics but supportive care helps birds recover.
Important note: chickens that recover from many respiratory infections become lifelong carriers. They look healthy but can spread the disease to other birds and pass it through hatched eggs. This is why introducing new birds without quarantine causes so many problems.
2. Coccidiosis
Coccidiosis is a parasitic infection that primarily affects young birds, though adults can also develop it. It’s one of the most common causes of death in chicks and one of the easier conditions to recognize once you’ve seen it.
What to look for: Bloody or unusual droppings — sometimes pink, red, or rusty-colored. Lethargy. Reduced appetite. Hunched posture with ruffled feathers. Pale comb and wattles. Young chicks may suddenly die without much warning of illness.
What causes it: Protozoan parasites called Eimeria species, which live in the intestinal tract. The parasites spread through droppings, so wet bedding and crowded conditions accelerate transmission. Stress and unsanitary conditions trigger outbreaks.
What to do: Coccidiosis responds well to treatment if caught early. Corid (amprolium) is the standard treatment, administered in drinking water for 5-7 days. Most feed stores carry it. Medicated chick starter contains amprolium at preventive levels and reduces the risk for young birds.
Prevention matters more than treatment. Keeping brooder areas dry, not overcrowding chicks, and using medicated starter feed during the high-risk period (first 8-10 weeks of life) prevents most outbreaks. Adults usually develop resistance through normal exposure but can still get sick under stress.
3. Mites and Lice
External parasites are extremely common and one of the issues most likely to be missed because the parasites themselves are small and hide in feathers. The symptoms develop gradually enough that they’re easy to attribute to other causes.
What to look for: Decreased egg production. Lethargy and pale combs from blood loss (especially with red mites). Birds picking at themselves constantly. Feather damage, especially around the vent. Visible parasites — small dark or red specks moving on skin or feathers. Reddish or whitish debris around feather bases.
What causes it: Red mites (Dermanyssus gallinae) live in coops and feed on birds at night, then hide in cracks during the day. Northern fowl mites live continuously on the bird. Lice are larger than mites and visible on inspection.
What to do: Treatment varies by parasite. For active infestations, permethrin-based poultry dusts applied directly to birds work for most parasites. Permethrin spray on coop surfaces handles red mites that hide in the structure. Diatomaceous earth provides some preventive effect but isn’t strong enough for established infestations. Severe cases sometimes require ivermectin treatment under veterinary guidance.
Prevention through regular dust bathing access, periodic coop deep cleaning, and quarantine of new birds prevents most parasite problems.
4. Worms (Internal Parasites)
Internal parasites affect most outdoor flocks at some level. Many birds carry low parasite loads without obvious symptoms, but heavy infestations cause significant problems.
What to look for: Weight loss despite eating normally. Pale combs and wattles. Reduced egg production. Diarrhea, sometimes with visible worms in droppings. Birds with bloated abdomens despite weight loss. Stunted growth in young birds. Death in extreme cases.
What causes it: Several worm species infect chickens — roundworms (most common), cecal worms, tapeworms, and others. Birds pick up worm eggs from contaminated soil, primarily where droppings accumulate. Wet, crowded conditions accelerate the cycle.
What to do: Deworming with appropriate medication. Fenbendazole (Safe-Guard) and ivermectin are common options. Treatment timing matters because most dewormers require egg withdrawal periods. Some flocks need treatment every 6 months in heavy-pressure areas, others rarely need treatment. Fecal testing through a vet identifies which worms are present and confirms whether treatment is needed.
The natural approaches — pumpkin seeds, garlic, certain herbs — have limited evidence supporting actual deworming effectiveness. They may provide mild benefits but shouldn’t replace actual treatment for significant infestations.
5. Egg-Bound
Egg binding occurs when a hen has trouble passing an egg. It’s a serious situation that can be fatal within 24-48 hours if not addressed.
What to look for: A hen acting normal until she suddenly looks ill. Straining or appearing to push without producing an egg. Walking like a penguin or with a wide stance. Going in and out of the nest box repeatedly without success. Lethargy and refusing food. Sometimes a visibly distended abdomen.
What causes it: Various factors — calcium deficiency causing weak shell formation that doesn’t move properly, abnormally large eggs, double-yolked eggs, reproductive tract abnormalities, obesity, dehydration, age (very young or very old hens). First-time layers and older hens are at higher risk.
What to do: Move the hen to a warm, quiet location. Provide a calcium boost — crushed Tums, liquid calcium supplement, or oyster shell mixed with water. Warm baths can help — soak the hen’s lower body in warm water for 15-20 minutes, which relaxes muscles. Gentle massage of the abdomen sometimes helps. Lubricating the vent with mineral oil or vegetable oil can ease passage.
If the egg doesn’t pass within a few hours of these interventions, veterinary care is needed. In severe cases, the egg may need to be broken in place (carefully) or surgically removed, both of which carry risks.
Prevention through adequate calcium (free-choice oyster shell), proper nutrition, and managing weight reduces but doesn’t eliminate the risk.
6. Sour Crop and Impacted Crop
Crop problems are common and easy to recognize once you know what to look for. The crop is a pouch at the base of the neck where food is stored before being digested.
Sour crop symptoms include a soft, squishy crop that doesn’t empty overnight. Foul-smelling breath. A foul liquid that may regurgitate when the bird is held upside down. Lethargy and decreased appetite.
Impacted crop symptoms include a hard, full crop that doesn’t empty. The crop feels firm rather than squishy. Bird may still try to eat but the food doesn’t go anywhere. Eventual weight loss and weakness.
What causes them: Sour crop is usually a yeast (Candida) overgrowth, often following antibiotic use, prolonged wet weather, or contaminated food. Impacted crop occurs when something blocks the crop — long grass, bedding eaten while foraging, or stringy materials are common culprits.
What to do for sour crop: Withhold food for 12-24 hours. Massage the crop gently to break up contents. Some keepers tip the bird forward to drain the foul liquid, but this carries aspiration risk and should be done carefully. Apple cider vinegar in water (1 tablespoon per gallon) may help restore proper pH. Antifungal treatment with nystatin from a vet handles severe cases.
What to do for impacted crop: Withhold solid food. Provide olive oil orally (a few drops, several times daily) to help lubricate contents. Massage the crop gently. Some impactions resolve with these conservative measures. Surgical removal is sometimes necessary for stubborn impactions and is something some experienced keepers do themselves with proper preparation, though most prefer veterinary care.
Prevention involves limiting access to long grass, avoiding stringy materials, and providing grit for proper digestion.
7. Bumblefoot
Bumblefoot is a staph infection of the foot pad. It’s common, often missed for too long, and progressively harder to treat the further it advances.
What to look for: A dark scab on the bottom of the foot, often round. Limping or favoring one foot. Swelling of the foot. Heat in the affected area. In advanced cases, severe swelling extending up the leg.
What causes it: Bacterial infection (usually Staphylococcus aureus) entering through a small cut, splinter, or pressure point on the foot. Roosts that are too high, hard landing surfaces, or rough perch materials increase risk. Heavy breeds are particularly prone because of the impact stress on their feet.
What to do: Early cases sometimes resolve with daily soaking in warm Epsom salt solution and topical antibiotic ointment. More advanced cases require removing the infected core, which involves softening the scab through soaking, removing the dark plug of infected tissue, cleaning the wound, packing with antibiotic ointment, and bandaging. This is a procedure many backyard keepers learn to do at home, though the first time is intimidating.
Prevention through appropriate roost heights (lower for heavy breeds), smooth perch materials, soft landing surfaces, and keeping foot litter clean reduces incidence.
8. Marek’s Disease
Marek’s disease is a viral condition that causes paralysis and tumors. It’s common, often fatal, and worth understanding because it affects flock management decisions.
What to look for: Progressive paralysis, often starting in one leg. The classic “splits” posture with one leg forward and one back. Drooping wings. Irregular pupils or vision problems. Tumors visible as lumps under the skin in advanced cases. Sudden death in some cases.
What causes it: A herpesvirus that’s nearly universal in chicken populations. Most birds are exposed but only some develop clinical disease. Stress, genetics, and viral strain all influence whether exposure leads to illness.
What to do: There’s no treatment for Marek’s once symptoms appear. Supportive care for affected birds rarely results in recovery. Most birds with clinical Marek’s are eventually euthanized.
Prevention through vaccination is the only real protection. Marek’s vaccine is given to chicks at the hatchery, usually for a small additional fee. Once exposed, vaccinated birds may still carry the virus but don’t develop disease. Hatchery-vaccinated chicks are strongly recommended for new flocks. Adult birds can’t be vaccinated effectively after exposure.
The decision to cull Marek’s-positive flocks is sometimes recommended to prevent ongoing transmission, but practical realities make this difficult for many backyard keepers. Working with what you have through vaccination and stress reduction is more realistic.
9. Egg Yolk Peritonitis
This is a reproductive issue more common in older laying hens and in heavy laying breeds. It’s serious and often fatal without treatment.
What to look for: Lethargy and depression. Swollen, fluid-filled abdomen (sometimes described as feeling like a water balloon). Penguin-like stance. Reduced or stopped laying. Decreased appetite. Pale or yellowish comb. Difficulty breathing in advanced cases.
What causes it: An egg or yolk material gets released into the abdominal cavity instead of moving through the reproductive tract. The yolk material causes infection and inflammation, sometimes accumulating significant fluid. Older hens, obese hens, and high-production breeds are at higher risk.
What to do: Treatment typically requires veterinary care. Antibiotics, draining of accumulated fluid, and supportive care can help in some cases. Hormone implants that suppress laying are sometimes used in valuable pet hens to prevent recurrence.
Without treatment, the condition progresses to death. With treatment, outcomes are variable — some birds recover, others have chronic issues. The decision to treat or euthanize involves quality of life considerations alongside practical factors like cost and availability of veterinary care.
Prevention through maintaining healthy weight, providing adequate nutrition, and avoiding excessive treats reduces but doesn’t eliminate risk.
10. Heat Stress
Heat stress isn’t strictly an illness but a condition that can become an emergency rapidly during hot weather. Recognizing the signs and responding quickly prevents deaths.
What to look for: Open-beak breathing and panting. Holding wings away from the body. Pale combs and wattles. Lethargy or extreme inactivity. Refusing to eat. Sitting splayed out on cool surfaces. Reduced or stopped laying. In severe cases, seizures or sudden death.
What causes it: Inability to dissipate body heat in hot weather. Chickens can’t sweat — they rely on panting, dissipating heat through their combs and feet, and avoiding heat-generating activity. Heat above 90°F with high humidity is dangerous for most breeds, and very dangerous for heavy fluffy breeds like Cochins, Brahmas, and Orpingtons.
What to do during active heat stress: Immediate cooling. Provide shade if not already available. Cool (not cold) water for drinking, refilled often. Shallow pans of cool water for birds to stand in — they lose significant heat through their feet. Frozen water bottles placed in the run for birds to lean against. Fans for air movement. Misters in extreme situations. Wet, cool towels to wrap around overwhelmed birds.
Prevention requires anticipating hot weather. Adequate ventilation in coops. Shade in runs. Multiple water sources. Avoiding handling or moving birds during peak heat. Reducing protein-heavy treats that increase metabolic heat. Considering breed selection for hot climates — Mediterranean breeds handle heat far better than fluffy ornamentals.
Common Mistakes With Chicken Health
Several patterns repeat with new keepers approaching illness:
Hoping problems resolve on their own. Most chicken illnesses don’t improve without intervention. Waiting to see if a sick bird gets better usually wastes the window when treatment would be most effective.
Not isolating sick birds. Continuing to keep a sick bird with the flock spreads disease and makes individual care more difficult. A separate space, even temporary, helps the sick bird and protects the others.
Diagnosing from internet symptom lists alone. Many chicken illnesses share early symptoms. Specific identification often requires examining the bird, considering the flock history, and sometimes testing. Internet diagnosis as a guide is fine; internet diagnosis as a final answer often misses things.
Skipping quarantine for new birds. Introducing untested new birds spreads diseases through established flocks. A 30-day quarantine in a separate space catches most problems before transmission occurs.
Inadequate biosecurity. Things like wearing the same shoes between coops, sharing equipment without disinfection, or visiting other flocks and returning without precautions spread disease unnecessarily.
Not having basic supplies on hand. A small first-aid kit with vetrap, antiseptic spray, electrolytes, basic medications, and other supplies prevents the panic of needing something at 11 PM when stores are closed.
Avoiding veterinary care until it’s too late. Many situations resolve well with prompt veterinary attention but become unmanageable with delay. Knowing where local poultry-knowledgeable vets are before an emergency saves time when it matters.
Frequently Asked Questions
How do I know when to euthanize versus treat? Quality of life and likelihood of recovery are the main factors. Birds that are suffering with little hope of improvement may be better off euthanized humanely. Birds with reasonable recovery prospects warrant treatment. Some situations are genuinely difficult judgment calls without clear right answers.
Can I give chickens human medications? Some, with appropriate dosing. Others are toxic. Aspirin and certain antacids have specific uses in poultry. Many other human medications shouldn’t be used. Consulting poultry-specific resources or veterinary guidance before administering anything is the safer approach.
Are chicken vaccines worth it? For Marek’s disease specifically, yes — the disease is common and devastating, the vaccine is cheap, and protection is real. Other vaccines (Newcastle, infectious bronchitis) have variable value depending on local disease pressure.
Should I keep a chicken first-aid kit? Yes. Basic supplies including vetrap, antiseptic, electrolyte solution, Corid, permethrin powder, syringes for oral medication, and Epsom salts handle most common situations. Adding to this kit over time based on what you’ve needed prevents repeated emergencies.
Are backyard chicken vets actually available? Variable by location. Some areas have excellent avian or poultry vets. Others have only large-animal vets unfamiliar with chickens. Finding local resources before you need them — calling around to ask which clinics see chickens — prepares you for emergencies.
What about home remedies and natural treatments? Many traditional approaches have some basis but limited evidence. Some work well (apple cider vinegar in water, garlic, herbs) for mild support. Some don’t work for serious conditions despite popular claims. Using natural approaches as supplements to proven treatments is generally fine; using them as replacements for actual treatment of serious problems is risky.
How can I tell normal weird chicken behavior from sick behavior? Time and observation. Normal behaviors include dust bathing (looks alarming first time), broodiness (sitting fixated in nest box), molting (looking ragged), and various other patterns. Sick behavior involves changes from a bird’s normal pattern, not just behaviors that look strange to humans. Knowing your individual birds matters more than any general checklist.
Building Recognition Over Time
Recognizing chicken illness is partly knowledge and partly experience. The knowledge piece — knowing what specific conditions look like and what to do about them — comes from resources like this one and other reading. The experience piece — knowing what your specific flock looks like when healthy versus subtly off — comes from time spent observing birds and developing a sense of their normal patterns.
Most experienced chicken keepers can spot a sick bird from across the yard before any specific symptom is obvious. The bird stands a little differently, holds its tail a little lower, moves a little slower than usual. These subtle changes become recognizable through familiarity with healthy behavior.
For new keepers, the most useful approach is daily observation of the whole flock. A few minutes watching birds at feeding time, during morning activity, and as they settle for evening reveals problems while they’re still treatable. Building this routine into daily activities makes problems easier to catch and respond to.
The flock that thrives over years isn’t the one whose keeper has memorized every disease. It’s the one whose keeper notices the subtle changes early, responds appropriately, maintains good basic husbandry, and has resources available for the situations that exceed basic care. That combination handles most of what backyard chicken keeping presents over the long run.