Dog Skin Darkening Belly. Dog skin discoloration on belly due to bruising is quite common due to the thin coat of fur covering the area. Flea allergy dermatitis (fad)is the number one cause for itching of hind quarters and hind legs with hyperpigmentation.
This dark skin discoloration in the belly and groin area is a classic pattern of skin change seen in dogs that have chronic skin irritation. The cause is usually a reaction to the season, obsessive scratching and biting, or to the sun. Just as a suntan protects our skin from the sun, so dark pigments are a protective reaction in dogs’ skin.
