The main difference between dog eye allergies vs. infection is that dogs can get allergies from environmental factors (i.e., food, pollen, house fleas). In contrast, a dog can get eye infections from bacteria, viruses, fungus, or trauma to the eye. Allergies are often mistaken for an eye infection due to the similarity in their symptoms. Symptoms Allergies Infection; Watery (translucent) X: Watery (with pus-like discharge) X: Inflammation: X: X: Excessive tearing: X: X: Squinting: X: X ...