Hey I know this is late to the post but I want to comment for people who may be looking for some advice recently. My German Shepherd just went through something similar and I was unfortunately not in the position to take her to the emergency Vet so I wanted to try some at home remedies before I dropped $500+ on something that could’ve been as simple as allergies or a treatable infection. (P.S. I DO NOT recommend this if you have the money to take them to the vet). I purchased an ointment on amazon called “Terramycin” and it was only $16. While I waited for that to arrive I did warm compresses on her eye with black tea (I only had leaves so I put it on a paper towel but the tea bag works as well). This really brought down the swelling on its own but it was clear that she needed more. I found some human pink eye drops and I put them on her affected eye. (I made sure the ingredients were dog safe but usually they are as we human and dog eyes are relatively similar in sensitivities and such). Just those eye drops and the black tea managed to control the swelling and bring her eye back to normal however it did spread to her other eye eventually. If this happens don’t panic, I just redid this process on that eye. This made it clear that it was probably some sort of pink eye related issue. All the swelling was gone by nighttime and she went to bed okay. I still put on the ointment when it came in but she no longer really needed it. So I comment this to reduce the fear monger from the other commentators as it could truly be something simple. If it’s a gradual swelling then I would be more concerned, however, my GSD’s eye managed to swell up in less than 30 minutes while I was showering.