There are different types of conjunctivitus that appear in dogs. Serous (clear watery discharge), keratoconjunctivitis sicca, where the tear ducts do not produce enough tears, Allergic conjunctivitis, Follicular conjunctivitis, Purulent conjunctivitis (when serous gets infected & pussy).
The red flag here is that it's recurring. If you have not had the dog to a vet or better yet, an eye specialist, to determine what's going on with the eyes, that's the first step. If left untreated, glaucoma, even blindness can happen. A basic serous conjunctivitis can be treated by rinsing the eye with sterile saline eyewash several times a day. Other cases can be treated with eye drops & ointments prescribed by your vet. This would be the step to take after a vet has confirmed what kind of conjunctivitis the dog has going on.
Hopefully it's a seasonal thing, and just the milder serous conjunctivitis, but always better to get it checked out :)
