Conjunctivitis is one of the most common eye problems in dogs. It has myriad causes that affect how severe and infectious the disease is. If caused by allergies or irritation, conjunctivitis isn’t contagious. If a virus or a bacterium is the culprit, the condition can be spread to other dogs.
The lining inside a dog’s eyelids is the conjunctiva. When this lining becomes inflamed, it’s called conjunctivitis or pink eye. Symptoms include red eyes and discharge that makes your dog blink frequently. When infection is present, discharge can seal the eyes closed. Dogs usually get conjunctivitis in both eyes, but sometimes only one eye is affected.
The cause of conjunctivitis determines whether it is infectious. Allergies often cause noncontagious conjunctivitis. If only one eye is affected, it’s likely something foreign irritated the conjunctiva. Pinkeye's most common cause is dry eyes due to inadequate tear production. Pinkeye is contagious only if it is caused by a virus or bacteria that causes purulent conjunctivitis. The distemper virus, which can lead to pinkeye, is very contagious. Staphylococcus and streptococcus are two bacteria that promote infectious purulent conjunctivitis. Infectious conjunctivitis is common in puppies but rare in adult dogs.