Why do I get watery eyes for no reason?

WAtering. Watering eyes often reflex tearing from eye irritation from dry eyes, blepharitis, or allergies.. One eye tearing may be nasolacrimal duct obstruction.
Dry eyes. Normal tears are not just water; they contain proteins that the eyes need to function properly. If you don't make enough normal tears, the eyes get irritated and you produce more of a watery substance that doesn't sooth the eyes properly. You can try using artificial tears 3-4 times a day to start, but if that doesn't help, see an ophthalmologist.