What is Conjunctivitis in cats and dogs?

Conjunctivitis, commonly known as pink eye, in cats and dogs is an inflammation of the conjunctiva, the membrane that lines the eyelids and covers the white part of the eye.  

What causes conjunctivitis in pets:

• Bacteria (like Staphylococcus aureus, Streptococcus), viruses (like feline herpesvirus), and in some cases, fungi.  

• Allergies: environmental allergens (pollen, dust, mites), or food allergies can trigger conjunctivitis.  

• Irritants: foreign bodies (like grass or sticks), chemicals, smoke, or even eye ointments can cause irritation.  

• Dry eye (Keratoconjunctivitis Sicca): insufficient tear production can lead to conjunctivitis.  

• Other conditions: eyelid abnormalities (entropion, trichiasis), trauma, or underlying diseases can also contribute to conjunctivitis.  

Written by Dr. Mariella Roberts, Veterinary Surgeon, Animal Trust Vets CIC | Published June 2025 | Review date June 2027 | This advice is for UK pets only and is not a replacement for seeing a vet