How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Dr.Beth Your Own Question
Dr.Beth, Dog Veterinarian
Category: Dog
Satisfied Customers: 631
Experience:  Doctor of Veterinary Medicine, University of Minnesota
Type Your Dog Question Here...
Dr.Beth is online now
A new question is answered every 9 seconds

My dog has a black spot on his tail. Been there for months

Customer Question

My dog has a black spot on his tail. Been there for months now. My vet perscribed antibiotics a while back but it did nothing. I think he called it a fox tail (I could be wrong on that because those are the thorns they get in their paws and I know it's not the same thing) but there was a term he used. It doesn't seem sensitive at all for the dog or seem to bother him, but it is kind of ugly. Any ideas?
Submitted: 8 years ago.
Category: Dog
Expert:  Dr.Beth replied 8 years ago.
I often see this kind of spot on the tails of dogs that have Hypothyroidism (low thyroid levels). The tail will have an area of hair loss, the skin will turn a black color and it is not itchy or painful for the dog. You will need your vet to run a T4 and TSH blood test to diagnose this condition.

Other possible causes that should be ruled out would include a fungal infection (like ringworm) and a mite infection (like Demodex). Your vet can test for these infections as well.

The final cause that I see sometimes in large breed dogs, is that this is similar to a callus. If your dog tends to fold its tail under and sit on it (especially on hard or rough surfaces), this habit will cause hair loss and the skin to toughen into a callus in the area.

Please let me know if I can be of further help.

Dr. Beth