Swollen eye

Bee

My 6 month old baby keeps waking up with his left eye swollen. After every nap. I went to the doctors yesterday but by the time our app came around the swelling had gone down 🙄 she said it could be a change in seasons with the pollen. I’ve not changed washing powder, his sheets are washed twice a week, we don’t have pets and he is generally very healthy... apart form teething. Any advice what it could be from?! Google keeps telling me it’s conjunctivitis but it’s not!