What causes a greasy cat tail with dark patches? Is it serious?

Hi there and thank you for using Petco Pet Education Center, formerly Petcoach to address your concern. From your description, it sounds as though he is dealing with a condition called seborrheic dermatitis. In this condition, there is excessive sebum (the greasy stuff) that accumulates on the skin and hair, leading to inflammation / hair loss. I would recommend having a veterinarian take a look at him so that the most appropriate diagnostic testing and treatment recommendations can be made. I would recommend using a shampoo that contains Benzoyl Peroxide (such as Dermabenz) and bathe him twice weekly until this resolves. I hope this helps guide you in the right direction! Please let me know if you have any other questions or concerns and I would be more than happy to help you further!

Flaky skin could be a sign of allergies, some hormonal diseases like hyperthyroidism, poor nutrition or even fleas. If there is no hair loss and her skin appears normal otherwise you could ask your veterinarian about using an oral fish oil supplement to see if that helps. If there is any hair loss, red skin or scabs I would recommend having her examined by your veterinarian. Unfortunately cats tend to lick most topical products so I do not typically recommend using them. There are some 'mousses' that absorb quickly that you could try, I like this brand: https://www.amazon.com/Douxo-Seborrhea-Mousse-Dogs-Cats/dp/B009TXE0KU

This sounds like a condition called "stud tail", quite common in cats and is believed to be an hormonal imbalance causing the skin to secrete oily substance that manifest itself as black dot, mainly in the tail but not only (the chin is also a common area). there is no effective treatment for this and the condition is not dangerous and usually does not bother the cat, some special shampoos can help in some cases (such as sebocalm for example).

Thanks for using Petco Pet Education Center, formerly Petcoach! This is possibly due to allergies. It really comes down to figuring out what is causing him allergies so that they can be treated or the specific allergen avoided. A secondary infection is likely and also needs to be addressed. Even if you have not being able to see fleas, this could still be flea dirt but I agree that it is less likely. There are many things that can cause allergies though in most cases they can be broken down into 3 big categories: flea, food and environmental allergies. Allergies are usually worked up in a stepwise fashion starting with flea allergies as this is the easiest and cheapest to take care of. If not on a flea preventative, then it would be a good idea to get started on one. If already on one then it would be a good idea to change to something else (there are many new products out in the market). If not improved in 1-3 months then it is time to move on and check for food allergies by switching to a novel diet (new protein and new carbohydrate). If that does not seem to be the issue then you are left out having to check for environmental allergies which require blood and/or skin tests. Allergies can be very frustrating to deal with at first but so rewarding at the end when we are able to treat them effectively!

The most common cause of hair loss around the tail is from flea allergies so I would definitely check her thoroughly for fleas. Other possibly causes are anal gland problems, seasonal allergies, ringworm, mites, infections. She should be examined by a vet to determine the cause and appropriate treatment.

It looks like an area of bacterial skin infection. Ringworm might be another possibility. I’d recommend having your vet examine your cat in person to determine what this might be. If they are suspicious of ringworm they might recommend a fungal culture.

A flea allergy often causes irritation at the tail base or top of the tail. It could be some other cause of inflammation as well, but I would recommend that you start her on a good monthly flea product if she's not already on something. You can try a product such this: https://www.petco.com/shop/en/petcostore/product/zymox-spray-with-5-hydrocortisone. Also, put an e-collar on her to prevent her from licking at it; and if its not improving within a few days, arrange for her to see a vet. You may be able to find a house call vet or mobile vet in your area who would come to your home, this may make it easier for you both. Thanks for asking PetCoach!