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Why is my senior dog's skin rash turning black and crusty now?

Updated on September 23rd, 2025

Pet's info: Dog | Border Terrier | Female | spayed | 10 years and 10 months old | 19 lbs

My 10 Year Old Border Terrier bitch has had an increasing number of skin tags. She has had a red rash on the inside of her thigh/ belly for some time which has not been causing her any discomfort. This localised rash has now become crusty, raised and black. Should we see a vet immediately? Thanks

3 Answers

Most Helpful Answer

Answered By Jenny, DVM

Veterinarian

Published on November 22nd, 2017

If the rash and skin problems is spreading and getting worse, then it is worth see a vet. She may need a skin biopsy or sample to find out the cause. Skin tags are common in older dogs but rash that is changing is not. They may need to do blood work to see if there is an endocrine problem such as a low thyroid or cushings disease.

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By David Elbeze, DVM, MRCVS
Veterinarian
Published on June 24th, 2018
This is probably due to a severe allergy, although it could also be fleas or mites.

First of all, in order to rule out skin parasites, you will need to treat Princess with a high quality flea treatment (e.g advantage), then get her to the vet to perform a skin scrape - this might reveal an infection or a mite infestation.

If all of those came back negative, the next step is to treat the allergy symptomatically and try discovering the cause of the allergy.

Some medications can be given by the vet in order to repair the skin lesions (steroids and antibiotics). simultaneously you should start her on a prescription hypoallergenic diet for at least 2 months.
Hopefully you will see some results after all this, if not you and your vet should consider putting her on a long term allergy treatment (Atopica or Apoquel).
1Pet Parents found this answer helpful
Answered By Jennifer Summerfield, DVM CPDT-KA
Veterinarian, Certified Dog Trainer
Published on March 12th, 2017
Poor Sweety! There are a number of different things that can cause itchy, flaky skin - the black color is likely pigmentation due to chronic scratching in these areas. Some common possibilities would include allergies (food allergies, or an allergy to something in the environment), fleas, a bacterial or fungal skin infection, or skin mites (mange). Since I see that Sweety is an older dog, it's also possible that she has a hormonal problem like hypothyroidism or Cushing's disease that is contributing to her skin problems.

Treatment will depend on what the underlying problem is, so I would recommend taking her to the vet for an exam as soon as you are able to. He/she can do some simple skin tests as well as blood work if needed to help diagnose the problem and get her started on appropriate medication to treat it.
1Pet Parents found this answer helpful

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