What is causing dark and foul smelling skin on my Golden Retriever’s belly?

Question: 

My 7 yr old Golden Retriever has developed a blackening on her stomach back to her private area.  It has quite an odor and she licks it a lot.  I have seen our veterinarian who thought it was a fungus.  She gave me an antibiotic and a shampoo; neither has helped.  What do you think?

Answer: 

The Golden Retriever is a fantastic breed of dog. It is also one of the most common canine breeds seen by veterinary dermatologists. In most conditions, darkening of the skin (hyperpigmentation) is a common indicator of chronic inflammation due to underlying allergic skin disease (environmental, food, parasite) with concurrent secondary bacterial and/or yeast skin infection. Other potential causes include: Hormonal disease (Hypothyroidism, Hyperadrenocorticism), Demodicosis (Hair Follicle Parasite), Viral Infection, or Neoplasia. Secondary bacterial and/or yeast infections are very common in these regions. The use of a medicated shampoo and an antimicrobial medication were appropriately directed towards those potential conditions.  If the condition has failed to resolve, further diagnostics should be performed to ensure your dog does not have a resistant bacterial infection as well as pursuing an underlying diagnosis, as skin infections in dogs are usually not a primary disease, they are a secondary manifestation of a primary condition. An appointment with a veterinary dermatologist would be useful in determining the disease condition(s) for your dog, while working together with your veterinarian long-term to maintain your dog's cutaneous and overall health.