What is acanthosis nigricans?
Acanthosis nigricans is a condition characterized by a darkening and thickening of your dog’s skin. There are two forms of acanthosis nigricans:  primary idiopathic acanthosis nigricans and secondary acanthosis nigricans. Primary idiopathic acanthosis nigricans occurs mostly in short-haired dachshunds. Secondary acanthosis nigricans can be the result of allergies, a hormone imbalance in your dog or triggered by skin friction. This condition generally first develops in younger dogs of either sex.

What will acanthosis nigricans look like in my dog?
Generally you will first notice hair loss and darkened, thickened and rough skin under your dog’s armpit. In more serious cases, these symptoms will spread to other areas of your dog including the chest, front legs, abdomen, groin, ears and around the eyes.  As your dog ages and the condition progresses, your dog may develop secondary issues including bacterial or yeast overgrowth in the impacted areas.