Messy Bum :(

So recently, I've noticed Alcott's rear is...um...less than pleasant. I've had to take a warm paper towel to his area about two times a week or more (which he's just THRILLED about, let me tell you). Is there a reason he'd suddenly have a problem cleaning the area? Is there anything I can add to his food? It seems such a silly thing to make a special trip to the vet for, any advice would be much appreciated!

Is he overweight at all? Sometimes larger cats have issues with reaching properly to keep themselves clean.

Any changes in diet? A change in diet may cause his stool to taste differently, and he may find it unpleasant to clean himself.

Is his stool normal textured? Or has it been looser?

someone else may be able to offer other suggestions.

He's a big cat-- but he's always been, and the vet says while large he's not overweight. I wonder though if perhaps he's put on just an extra half pound or so, and that prevents him from cleaning himself? I haven't noticed any weight gain, but I'm not sure small weight gain would register with me. Perhaps I should switch him to low calorie and monitor his food for a while.
The only major change has been the addition of a dog to the household. They get along fine-- not buddies but not enemies by far. Other than that, his food is the same and his stool is the same as it's always been!

Your kitty isn't by chance a Manx, is he?

I would think that if his poops were "formed", his butt wouldn't be messy so it would seem that maybe his stools are more on the loose side?

What do you feed him? Has he by chance been getting at your dog's food? (you mentioned recently getting a dog). If so, it could be that the dog's food is causing more loose stools? Even if it's not something "in" the dog's food that's doing this directly, just the sudden "change in diet" of the dog's food can cause this; just like if a person switched their cat's food very suddenly.

Have you noticed your cat eating the dog's food?

Is there a way to put the dog's food somewhere that cat can't get at, see if this helps?