URGENT!! Stung by bee

[Goosebaby]

I’m sure it was a bee sting. I left the door open for his coop area and he approached the beehive area in my garden. I ran to him as I saw through the window but I was too late. The symptoms were instant. His eye shut straight away. However right now, his eye is more or less open, however there is a worrying grey/
Foggy layer on his eye

That sounds like swelling, worst case scenario he could have an infection brewing. Absolute worst case sometimes the eye will become necrotic and will have to be removed by a vet but that would be an extreme situation.

Have you tried the Benadryl?