What it may be?

I'm very worried right now. Lately, Kai has been licking his butt hole repeatedly. When I checked him, I discovered that the top of his butt hole is swollen and red.

Anyone with experience with this?

Could be glands or worms . I'd take in a stool sample .

I'm thinking impacted anal glands. Definitely call the vet.

My dog Peanut has the same problem. The first time it was the anal glands, but now it's not. He's got bad allergies when the pollen season starts and he licks away which irriates it. I have to give him Benedryl when his allergies are acting up.

If it's on top of the anus then I don't think it's an anal gland problem. They are situated underneath at about 5 and 7 o'clock (if that makes sense lol). When I first read your post I thought of external hemorrhoids but apparently it's quite uncommon in dogs. If it's still there in a few days I'd get it checked by a vet just to be sure.