What Causes Circles of Bumps Under a Dog’s Leg?

A ring or circle of bumps in the armpit has a few common causes. One of the most frequent is a bacterial skin infection (superficial pyoderma), which often starts as small red bumps or pimples and spreads outward in a ring with a scaly edge. Ringworm, a fungal infection, can also form rings and is contagious to other pets and people. Insect bites, allergies and contact irritation are other possibilities.

Mange is less likely to cause neat circles, though sarcoptic mange can cause itchy red bumps in the armpits and on the belly, and demodectic mange can cause bumps and hair loss.

Because these look alike but are treated differently, it's best to have your vet take a look, especially if the bumps are spreading, itchy, oozing or painful. Your vet may do a skin scraping, a quick look at skin cells under the microscope, or a fungal test. Until then, avoid putting creams on the area, wash your hands after touching it, and stop her from licking it. Read more about dog skin rashes and bumps.

This is general information, not a diagnosis. Please follow your own vet's advice.