Acne, also called chin pyoderma, puppy dermatitis, muzzle folliculitis, furunculosis or simply “pimples,” is a fairly common inflammatory condition that affects the lips, chins and muzzles of puppies and young adult dogs. Occasionally, acne shows up in the genital region, the area beneath the tail or on the flank. What causes acne in dogs is not well-understood. However, canine acne is similar to acne in teen-aged people. It usually starts as hard, purplish-red raised areas and blackheads at the site of hair follicles. Bacteria get into the plugged follicles and multiply, creating whiteheads, which are pimples filled with pus. While mild acne outbreaks usually don’t cause dogs much discomfort, severe acne can be extremely painful. It is important for owners to recognize the signs of acne, so that they can take appropriate steps to treat the condition and relieve their dog’s discomfort.