A healthy dog has a clear gaze, and the eyes do not have abnormal discharge. Causes of eye discharge can be for example street dust, allergies or bacteria. If your dog's eyes seem red and very irritated, consult your veterinarian.
A small amount of discharge in the dog's eyes is common. If the discharge changes its color and thickens, the probable cause is a bacterial infection. When infected, the eye is red and the dog might try to scratch or rub the eye. If you suspect conjunctivitis, contact your local vet.
Long coat can be a cause for eye problems
If the dog has a long coat, the hair can reach the dog's eye causing irritation. You can prevent the hair reaching the dog's eyes by clipping them regularly. Clean the dog's eyes regularly by wiping them with a cotton pad, and check the eyes for any excessive hair or other foreign objects.
Sometimes the dog's eyes are runny, and in some cases, the discharge can cause the coat close to the eyes to get dyed dark. If the discharge is substantial and sudden, there might be an infection causing it or the eye might be injured. In addition, some food allergies can also cause runny eyes. When the eye has an injury or infection, the dog doesn't prefer to keep the eye open. Every time an eye starts to discharge acutely, a vet must be consulted.
For some breeds, it is characteristic for the eyes to be a little runny. In these cases, you don't have to medicate the dog. Instead, you can clean the coat around the eyes carefully with a damp cloth or gentle cleansers that are sold in pet stores.