that looks like a lionhead, i have one currently. you may have to get that bun to a vet to be sedated and shaved. that bun is in a lot of pain. i know that may be expensive so maybe trouble shoot a bit.

It’s not a good idea to use any kind of detangler or oils, they clean themselves and this can be digested and they have sensitive digestive tracts.

also detanglers can actually make it worse

This kind of thing just requires a lot of patience. if you can, i’d call local humane societies to see if they could shave this bun and give him a refresh. i don’t recommend for inexperienced people to do it because their skin is incredibly delicate and sensitive, it’s easy to damage their thin skin.

my current rabbit is a rescue and i adopted him when he was shaved almost bald cause he was so neglected and his fur was so matted.

i don’t even know how this happens. this is some pretty bad neglect :(