What causes pink eye in dogs?

Original Question: Coco had been scratching his right eye for about a week now. I gave him some eye drops called Pink Eye Relief. It’s a natural eye drop containing euphrasia. It works for a little while but it comes back and he starts scratching again. I’m wondering if he has an allergy. Can you tell me what to do for him? There is no yellow puss or anything coming out, only mild tearing and it’s clear. Thank you. - Coco

Dec 24, 2018

Thanks for your question.

It’s obvious that there is inflammation of the conjunctiva at the very least. The causes for this can be:

Bacterial eye infection
Keratoconjunctivitis Sicca (Dry eye)
Trauma to the eye
Corneal ulceration
Viral infection
A foreign body below the eye
Allergic conjunctivitis (not common but possible)
Glaucoma
Other less likely possibilities

The fact that the treatment is not working doesn’t really tell us much information. It would be irresponsible of me to make a diagnosis since I can’t examine your dog or perform proper testing.

I recommend you visit your veterinarian for a physical examination and consultation. They can perform a fluorescein dye test to look for any corneal ulcers or trauma. A Schirmer tear test can be performed to determine if the condition of dry eye exists. They may choose to make an assumptive diagnosis based on the examination and start a treatment trial. If they continue with diagnostics, tonometry can be performed to determine the pressure inside the eye to evaluate for glaucoma. A swab of the eye and performing a culture and sensitivity and viral panel would help identify the particular bacteria or virus if an infection is suspected.