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My dog has black skin spots, skin tags, and discharge. Should I worry?

Updated On September 23rd, 2025

Pet's info: Dog | English Mastiff | Male | neutered | 5 years and 11 months old | 175 lbs

For about 4 weeks now, my English Mastiff (who's about 6 years old) developed a scaly rash with black spots in the center. My husband believes it's just a heat rash and has been spraying on an OTC itch relief for pets. The rash is not really scaly anymore but it's still black. Today I noticed two skintags on his penis that weren't there before and a milky discharge. He doesn't seem to be in pain and he doesn't itch that much. We don't have much money to take him to the vet if it's nothing.

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2 Answers

Most Helpful Answer

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Answered By Linda G, MS, DVM

Veterinarian

Published on August 28th, 2017

Hello, & thank you for using Petco Pet Education Center, formerly Petcoach. It is always a good idea to seek a hands on veterinary visit, especially as a dog ages & new questions about health arise. Based on your pictures, it is possible that the discolored areas are indeed a reaction to the heat rash. Dog skin will often respond with the production of dark pigments ( melanin ) especially when a condition becomes chronic. As long as the area is not showing signs of a moist dermatitis & there is no significant redness or inflammation, then you can continue to treat the area topically. Skin tags are a common benign polyp, again fairly common as dogs age. The discharge also is probably a benign & normal accumulation of secretions. If each or any of the above become more concerning, then it really is in Nemo's best interest to have things thoroughly looked at & dealt with early on. Take care.

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    Answered By Laura Johnson VMD

    Veterinarian

    Published on

    Hi, thanks for using Petcoach! Thanks for the pictures! The black circular areas o Nemo's skin indicated areas of chronic inflammation either from a resolved bacterial or yeast infection. I still see some areas that are active (red spots). The skin tags are likely unrelated the the skin infection. I have seen dogs with Cushing's disease and low thyroids have the increased pigmentation as well. You can start bathing him in a medicated shampoo to see if it helps. If he continue to scratch or new areas keep cropping up he should see your Vet. I've attached a link to a shampoo that I like. bathe him 2 times per week. Leave the lather on for 10 mins before rinsing. Good luck and I hope Nemo feels better soon! https://www.chewy.com/malaseb-medicated-shampoo-dogs-cats/dp/119232?utm_source=google-product&utm_medium=cpc&utm_campaign=hg&utm_content=Malaseb&utm_term=&gclid=EAIaIQobChMIr-TordD61QIVkzyBCh3vcwspEAQYASABEgLDB_D_BwE&gclsrc=aw.ds

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