My 3-week-old puppy has blotchy hair loss. What's causing it?
I would have this checked by a vet. It sounds very much like ringworm. Although the name suggests otherwise, ringworm is not caused by a worm at all-but a fungus. This highly contagious infection can lead to patchy areas of hair loss on a pet, and can spread to other animals-and to humans, too.
Classic symptoms of ringworm include lesions that typically appear on a pet’s head, ears, paws and forelimbs. These lesions can cause patchy, crusted circular “bald spots” that sometimes look red in the center. In mild cases of ringworm, there may be just a few broken hairs, while bad cases of ringworm can spread over most of a pet’s body. It’s also possible for a pet to carry the fungus and not show any symptoms whatsoever.
Treatment of ringworm depends on the severity of the infection. A veterinarian may prescribe a medicated shampoo or ointment that contains miconazole or a dip such as lime sulfur to kill the fungus. In some cases, oral medications are necessary to cure ringworm. In severe cases, it may be necessary to use a topical and oral treatment, in addition to clipping away the fur. Once treatment begins, lesions should begin to heal in about one to three weeks.
Please note, it is important to treat your pet for as long as recommended by your veterinarian. Even though the skin lesions may have cleared up, this doesn’t mean your pet is cured or can’t infect another animal or person. Certain diagnostic tests may need to be repeated in order to ensure cure. And unfortunately, there is no guarantee that reinfection won’t occur!
Updated on September 23rd, 2025