It’s typical for conjunctivitis in cats to have an infectious cause. The most common source is the viral infection, herpesvirus FHV-1. This virus can recur throughout your cat’s life, especially during times when she is highly stressed, on corticosteroids or if she has feline immunodeficiency virus.
Chlamydophila (a bacterial infection) is the second most common cause of conjunctivitis. Allergens and irritants, trauma to the eye, and disorders of the cornea, tear ducts or eyelid can also lead to conjunctivitis. Occasionally, there can be multiple explanations behind your cat’s conjunctivitis.
If the cause of your cat’s conjunctivitis is herpesvirus FHV-1, it can spread to other cats in your house (although not to humans), so treating it quickly is important.