Blepharitis in Horses

Blepharitis in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost
Blepharitis in Horses - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What are Blepharitis?

Any kind of trauma to the eye, whether penetrative or blunt, can create inflammation in the eye and eyelid. In addition, the damage from the injury can invite bacterial, viral, or fungal infection which will cause even more inflammation. Traumatic blepharitis may also develop into an eyelid abscess which will need to be treated with an aggressive antibiotic treatment. Insect bites may be a possible cause of infection and parasitic blepharitis so you should look for signs of insect bites around your horse’s eye. Blepharitis of all types can happen in any breed, sex, or age of horse, but is most common in juvenile horses up to a year old.

The most common cause of blepharitis, which is inflammation of the eyelids, is a bacterial infection after a penetrative injury. This is called infectious blepharitis, but there are other types such as fungal, parasitic, viral, and immune-related. This can be unilateral (affecting one eye) or bilateral (affecting both eyes) which can help the veterinarian determine the cause. Unilateral blepharitis causes include blunt trauma, self-trauma, insect or snake bite, foreign body, and abscess. Bilateral blepharitis includes self-trauma, systemic diseases, parasites, influenza, allergy, or lymphosarcoma.

Symptoms of Blepharitis in Horses

The first sign of blepharitis in horses is the swelling of the eye, of course. However, if it is secondary to a virus you will likely not notice the blepharitis as a separate condition. This depends on what virus your horse has such as influenza or equine papilloma, but the most common signs are:

  • Swelling of eyelids
  • Tearing (discharge) from the eye
  • Redness of the conjunctiva
  • Hair loss
  • Abrasions on the surrounding skin
  • Mucous drainage
  • Squinting
  • Pain
  • Trouble seeing
  • Dizziness


  • Bacterial blepharitis includes Staphylococcus spp., Mycoplasma spp., Listeria monocytogenes, Chlamydophila spp., and Moraxella spp.
  • Fungal blepharitis is commonly caused by Trichophyton spp., Histoplasma farciminosum, Cryptococcus mirandi, Fusarium, Aspergillus, and Penicillium
  • Parasitic blepharitis includes eyeworms (Thelazia lacrimalis), Typanosoma evansi, Draschia, Onchocerca spp., Ophthalmomyiasis spp., and stomach worms (Habronema)
  • Viral blepharitis is most often caused by EHV-1, EHV-2, Adenovirus, papillomas from a papovavirus, equine viral arteritis
  • Immune-related blepharitis includes allergic blepharitis, eosinophilic granuloma, pemphigus foliaceus, ad bullous pemphigoid


Causes of Blepharitis in Horses

  • Virus
  • Parasites
  • Injury to the eye with secondary bacterial infection
  • Fungus
  • Allergy


Diagnosis of Blepharitis in Horses

An optical examination will be performed after a physical assessment which will include vital signs and palpation of major organs and muscles. The veterinarian will always perform a complete physical analysis no matter what the reason for the visit may be, to look for underlying illnesses. The optical examination will include several diagnostic tests. Fluorescein and rose bengal stains should be used to detect eye injuries and corneal abrasions. A histologic examination will be done, which should show collagenolysis, mast cells, and eosinophils. Microbial culture and sensitivity test should be done to determine whether fungal or bacterial infection is present.

Biopsy of the neoplasia is helpful as well. Blood work usually includes a complete blood count and chemical panel, but will not show any abnormalities unless there is an underlying illness or disease. Dermal scraping, hair samples, and impression smears of the eyelid margins may be used to find parasites if they are suspected. Radiographs (x-rays) should be done to make sure there are no fractures or other abnormalities, especially if your horse’s eye problem was caused by injury.



Treatment of Blepharitis in Horses

Your horse’s treatment plan depends on the cause of the blepharitis and how serious it is. Medication is the most obvious choice for infections and surgery to repair lacerations or penetration injuries.


Larvicidal liquid is used for lesions on the lid and organophosphate eye drops with corticosteroids can be successful in treating most parasitic infestations. Antiparasitic drugs for parasites and antibiotics for bacterial blepharitis are the common treatments for these types of infections. Anti-allergens such as Zaditor are used to treat allergic reactions. Systemic anti-inflammatory ointment and eye drops are also used to treat the uncomfortable symptoms of any blepharitis. Nonsteroidal anti-inflammatory drugs (NSAIDS) will be given if the inflammation is severe.


If there is any kind of eye injury, the veterinarian will sedate your horse to clean up and repair any damage done to the eye and eyelid as well as the area around the eye. Debridement is usually done to rid the area of any damaged tissue. Topical antibiotics and eyelid lubricants will be prescribed to prevent further infection.



Worried about the cost of Blepharitis treatment?

Pet Insurance covers the cost of many common pet health conditions. Prepare for the unexpected by getting a quote from top pet insurance providers.

Recovery of Blepharitis in Horses

Follow up will be required. An eye injury or infection can quickly turn to a serious situation with possible loss of vision; the veterinarian will want to ensure that the eye and eyelid issue is completely resolved before giving you the go ahead to return your horse to normal activity.



Blepharitis Questions and Advice from Veterinary Professionals

Need pet insurance?
Need pet insurance?

Learn more in the Wag! app

Five starsFive starsFive starsFive starsFive stars

43k+ reviews


© 2022 Wag Labs, Inc. All rights reserved.