Pictured below is a young Boxer with a swollen lower eyelid. His foster mom let him out to play in the backyard and he returned looking like this. Other than a swollen eye, this pup is in good health. List the most likely causes of this condition then scroll down for the answer.
Diagnosis: The most common causes are: 1) Allergic reaction usually from an insect. 2) Ocular foreign body causing patient to rub eye. 3) Infection
Below is the foreign body I removed from his eye. It looked like a piece of a plant stem. I found it hiding behind the third eyelid. Ouch!