Skin infection?

Before someone says this, I have made a vet appointment for my cat, I am just curious about what this could be.

I have a medium haired black and white, and his hair is so long in some places that he has trouble grooming himself well enough, so, naturally, I brush him and use cat wipes or even give him a bath when he needs it. About a month and a half ago I noticed that the hair at the base of his tail was really greasy--almost to the point of being goopy. When I looked down into his skin, I noticed a brown, greasy substance coating his skin in that area. I brushed him out, gave him a thorough bath with some antibacterial cat shampoo, and was sure to get at least that area really dry with a hair dryer. I thought it had been taken care of.

A few weeks later, I noticed that it had come back, and seemed to be worse this time. Does anyone have any idea what this could be and what I could do in the meantime?

The area does not seem itchy or irritated for my cat, he just cleans as usual

Skin infection?

Its called Stud Tail.

Is her Neutered?

If he is the vet will have some other ideas for treatments. if is not get him fixed and it will get better.

Oh ya if you do nothing his hair will begin to fall out it will look just awful.

Skin infection?

If the goop is under his tail, it could be poop that gets stuck to his fur. If it's on top of his tail, he could be over grooming. Sometime long-haired cats obsessively groom because they can't reach certain areas. My last thought is that it might be a hot spot, but since it doesn't seem to be bothering him, it's not likely. Take him to the vet and see what they have to say.

I have a Standard Poodle who gets blocked pores, and the pus that comes out ranges from white to black, so maybe there are some blocked pores that are causing this.