The following is an excerpt from the Petfinder Blog.
Q: My Chihuahua is developing dark skin patches under her front leg and on her tail. What causes these black patches?
Could it be fleas?
A: Sometimes these dark patches can be normal. They can occur in areas of friction (under legs, armpits) or they can be normal pigmentation in your dog’s skin that occurs with age.
Dogs with severe skin allergies can develop black patches but the skin in that area is thick, itchy, and almost like elephant skin. That is called lichenification and it is caused by inflammation.
Fleas typically do not cause dark patches but will cause hair loss along the back of the hind legs. Your dog would also be itchy if there were fleas. Make sure to get a good monthly flea preventative from your veterinarian.
If these dark skin patches seem dry or troublesome to your pet, it may be a good idea to have your vet take a look.
If you have questions about your pet’s health, you can submit them to Dr. Lauren at firstname.lastname@example.org.