Red butt

Hello !
One of the strays I care for has his butt (the asterisk) red and a little swollen.
I asked the vet what can I do and he said to give him a drontal for worms and to put a cream called Celestoderm with Garamycin.
Does anyone know why is his butt like that?

If a cat has severe diarrhea for an extended period of time, it can cause the anus to become inflamed. Worms can cause diarrhea...but so can a lot of other things. Anyway of getting him into the vet? But the cream your vet suggested really does help with the inflammation and pain. Now getting it on there...that's a whole different ballgame, .

Well, I'm not sure if the red swollen butts looked the same...

But when my cat had the same symptoms it was due to swollen glands and I had to, uh..., release them. Not fun at all! But the boy was fine the next day and haven't had an issue again though I know it can be a recurring problem.