The dog may be crying because his eyes are irritated. Things like dust, dirt, hair, or other foreign objects may irritate your dog's eyeballs, causing them to produce more tears to flush and clean their eyes. In addition, some eye diseases, such as keratitis, conjunctivitis, etc., may also cause moist eyes in dogs.

In addition to eye irritation and disease, moist eyes in dogs may also be related to their emotional state. For example, when dogs feel anxious, nervous, or uneasy, their bodies may release some stress hormones, which may affect the secretion of tear glands, causing moist eyes.