Reoccuring Conjunctivitis

Hi all,

My dog has grass allergies, so after I take him out I would rinse him with water. I don't use shampoo to retain his natural oils.
That seems to prevent his itchy body and he doesn't get hives anymore.

However, every 2 months he would start pawing at his eyes which leads to conjunctivitis. I've been wiping his eyes with warm (slightly salted) water every day, but it doesn't seem to prevent the eye itchiness.

I always take him to the vet when it happens and he always gets a steroid injection and antibiotics. But this doesn't seem sustainable if I need to take him to the vet every 2 months.
If he takes too many antibiotics, his immunity may resist it over time.

I'm not sure if anyone in this forum has had similar problems?
And is there a natural way to prevent conjunctivitis that I could try?

Cheers,
Sandra