Conjunctivitis in Chickens: Causes of Swollen, Runny or Closed Eyes

Quick Answer
  • Conjunctivitis means inflammation of the tissues around the eye. In chickens, it often shows up as redness, tearing, foamy discharge, swelling, crusting, or one eye staying partly closed.
  • Eye problems in chickens are often linked to a bigger issue, not only the eye itself. Common causes include respiratory infections such as infectious coryza or Mycoplasma gallisepticum, irritation from ammonia or dusty bedding, trauma, and less commonly parasites or serious reportable diseases.
  • See your vet promptly if your chicken has facial swelling, trouble breathing, both eyes affected, thick pus, reduced appetite, a drop in egg production, or multiple birds with similar signs.
  • Isolate the affected bird from the flock while you contact your vet. Good ventilation, clean bedding, and strict biosecurity help reduce spread, but home care alone may not address the underlying cause.
  • Typical US cost range for evaluation and treatment is about $75-$350 for an exam and basic medications, with diagnostics and flock-level testing increasing total cost to roughly $200-$800+ depending on the cause.
Estimated cost: $75–$800

What Is Conjunctivitis in Chickens?

Conjunctivitis is inflammation of the conjunctiva, the thin tissue that lines the eyelids and covers part of the eye. In chickens, pet parents may notice watery eyes, redness, swelling around the eyelids, crusting, or an eye that stays partly or fully closed. Sometimes the discharge looks clear and mild at first. In other birds, it becomes foamy, sticky, or thick.

In backyard chickens, conjunctivitis is often a sign rather than a final diagnosis. The eye may be reacting to dust, ammonia from damp litter, pecking injury, or a respiratory infection affecting the sinuses and upper airways. Diseases such as infectious coryza and Mycoplasma gallisepticum can cause conjunctivitis along with nasal discharge and swelling around the face.

That is why a swollen or runny eye should be looked at in context. If one chicken has mild irritation after bedding changes, the problem may be local and limited. If several birds have eye discharge, sneezing, facial swelling, or reduced appetite, your vet will be more concerned about a contagious flock problem.

Early evaluation matters. Chickens can hide illness well, and eye disease may worsen quickly if the underlying cause is infectious or if thick debris builds up in the sinuses.

Symptoms of Conjunctivitis in Chickens

  • Watery, teary, or foamy eye discharge
  • Red or inflamed tissue around the eye
  • Swollen eyelids or puffiness below the eye
  • Eye partly closed or fully closed
  • Crusting, sticky debris, or thick discharge
  • Sneezing, nasal discharge, or noisy breathing
  • Facial swelling or swollen infraorbital sinus
  • Lethargy, poor appetite, weight loss, or drop in egg production

A mildly watery eye after dust exposure may improve once the environment is corrected, but chickens with worsening swelling, thick discharge, facial puffiness, breathing changes, or more than one affected bird should be seen sooner. See your vet immediately if your chicken is struggling to breathe, cannot open the eye, stops eating, seems weak, or if you notice sudden illness spreading through the flock.

What Causes Conjunctivitis in Chickens?

Conjunctivitis in chickens has several possible causes. Infectious causes are common and include upper respiratory diseases such as infectious coryza, caused by Avibacterium paragallinarum, and Mycoplasma gallisepticum infection. These conditions can cause eye discharge, conjunctivitis, sinus swelling, sneezing, and reduced flock performance. Viral diseases such as avian metapneumovirus can also affect the eyes and upper respiratory tract.

Noninfectious irritation is also important, especially in backyard flocks. High ammonia from wet litter, poor ventilation, dusty bedding, chemical irritants, and trauma from pecking or foreign material can inflame the eye. Merck notes that ammonia levels around 25-30 ppm can damage the upper respiratory tract, and higher levels can injure the cornea.

Less common causes include parasites affecting the eye, skin lesions near the eyelids, or secondary bacterial infection after irritation or respiratory disease. Because some serious poultry diseases can also cause swelling around the eyes and respiratory signs, your vet may recommend testing rather than assuming it is a minor eye infection.

The pattern in the flock matters. One bird with one irritated eye may point toward trauma or debris. Several birds with eye and respiratory signs make contagious disease much more likely, which changes both treatment planning and biosecurity steps.

How Is Conjunctivitis in Chickens Diagnosed?

Your vet will start with a hands-on exam and a flock history. Helpful details include how many birds are affected, whether signs started after new birds were added, bedding changes, ventilation problems, recent shows or swaps, contact with wild birds, and whether there are sneezing, nasal discharge, facial swelling, or egg-production changes.

The eye itself may be checked for debris, trauma, corneal damage, eyelid swelling, and discharge. Your vet may also examine the nostrils, sinuses, mouth, and breathing pattern because eye disease in chickens often overlaps with upper respiratory disease.

Testing depends on severity and flock risk. For suspected infectious coryza, diagnosis may involve bacterial culture or PCR. For Mycoplasma gallisepticum, PCR is commonly used, and culture may also be considered. In some cases, your vet may recommend swabs, bloodwork, cytology, or necropsy of a deceased flockmate to clarify the cause.

A diagnosis matters because treatment choices, isolation time, and flock management differ by cause. Supportive care may help comfort, but it does not replace identifying whether the problem is environmental irritation, a treatable bacterial infection, or a contagious disease that needs broader flock control.

Treatment Options for Conjunctivitis in Chickens

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$75–$180
Best for: A single bright, eating bird with mild watery discharge or mild swelling and no major breathing changes.
  • Office or farm-call exam focused on the affected bird
  • Isolation from the flock while monitoring appetite, breathing, and droppings
  • Environmental correction such as cleaner bedding, lower dust, and better ventilation
  • Gentle eye cleaning or flushing performed under your vet's guidance
  • Basic supportive medications if your vet feels they are appropriate
Expected outcome: Often fair to good when the cause is irritation or a mild early infection and the environment is corrected quickly.
Consider: Lower upfront cost, but limited testing means the underlying cause may remain uncertain. This can be risky if the problem is contagious or if more birds become sick.
Most Common

Recommended Standard Treatment

$180–$450
Best for: Most backyard chickens with persistent eye discharge, swelling, crusting, sinus involvement, or mild respiratory signs.
  • Veterinary exam plus flock history review
  • Targeted eye and respiratory assessment
  • Swabs or basic diagnostics when infection is suspected
  • Prescription medications chosen by your vet based on likely cause and local regulations
  • Written isolation, sanitation, and flock-monitoring plan
Expected outcome: Good for many uncomplicated cases when treatment starts early and flock management is improved.
Consider: More complete than conservative care, but still may not identify every flock-level pathogen. Some birds improve clinically yet remain carriers depending on the disease.

Advanced / Critical Care

$450–$800
Best for: Birds with severe facial swelling, closed eyes, poor appetite, breathing difficulty, repeated flock outbreaks, or cases where several birds are affected.
  • Comprehensive diagnostics such as PCR panels, culture, or additional laboratory testing
  • Assessment of multiple birds or flock-level consultation
  • Treatment for severe sinus swelling, dehydration, or breathing compromise as directed by your vet
  • Necropsy and laboratory submission of a deceased bird when needed
  • Expanded biosecurity and outbreak-control planning
Expected outcome: Variable. Many birds can stabilize with prompt care, but outcome depends on the specific disease, flock spread, and whether chronic carrier states are involved.
Consider: Highest cost range, but gives the clearest diagnosis and best flock-level decision support. Some contagious diseases may still require long-term management rather than a complete cure.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Conjunctivitis in Chickens

Bring these questions to your vet appointment to get the most out of your visit.

  1. Does this look more like local eye irritation, sinus disease, or a contagious respiratory infection?
  2. Should I isolate this chicken, and for how long?
  3. Do you recommend PCR, culture, or other testing for infectious coryza or Mycoplasma?
  4. What signs would mean this has become an emergency, especially overnight?
  5. Are there environmental changes I should make right away in the coop, such as ventilation or bedding changes?
  6. If one bird is sick, what should I watch for in the rest of the flock?
  7. Could this bird remain a carrier even if the eye improves?
  8. What treatment options fit my goals and cost range for this bird and the flock?

How to Prevent Conjunctivitis in Chickens

Prevention starts with flock environment. Keep bedding dry, reduce dust, and improve airflow so ammonia does not build up. Wet litter and poor ventilation irritate the eyes and airways, making chickens more vulnerable to secondary infection. Clean feeders, waterers, and high-contact surfaces regularly.

Biosecurity is also a big part of prevention. USDA recommends limiting visitors, washing hands before and after handling poultry, and cleaning and disinfecting equipment before it moves between bird areas. New birds should be quarantined before joining the flock, because apparently healthy carriers can introduce respiratory disease.

Try to reduce contact with wild birds and shared water sources when possible. If a chicken develops eye discharge or facial swelling, isolate that bird and contact your vet early. Fast action can reduce spread and may protect the rest of the flock.

Routine observation matters more than many pet parents realize. A small change in one eye can be the first clue to a coop problem, a contagious infection, or a management issue that needs correction before multiple birds are affected.

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