How to Determine if a Dog Has Ringworm

By Jane Meggitt

If you notice skin lesions on your dog, he could be suffering from the fungal infection known as ringworm. Because ringworm symptoms resemble those of other canine skin diseases, it's important to take your pet to the vet for diagnosis and treatment. Ringworm easily spreads to people, so if you develop lesions on your hands or other body parts, pay a visit to your doctor.

Ringworm Infection

Technically known as dermatophytosis, ringworm is a fungal disease. It received its nickname from the raised, usually round area of the lesions. In dogs, ringworm primarily affects puppies and debilitated canines, or those with a compromised immune system. The fungus affects the dead layers of the hair and skin, and sometimes affects the nails. It feeds on keratin, the material making up those layers. Once diagnosed, your veterinarian likely will recommend a combination of medication, regular anti-fungal shampooing and lime dips to combat the infection. You'll also have to disinfect your dog's living quarters with a bleach solution to kill the spores.

Ringworm Symptoms

Ringworm lesions most often appear on the face, head and front legs, although they can develop anywhere on the body. Generally, there's hair loss and scaly, circular sores. In some cases, dogs with ringworm exhibit folliculitis, or hair follicle inflammation. Less often, furunculosis, or skin boils, affect dogs suffering from ringworm. Dogs with a mild case of ringworm may remain asymptomatic, but they can spread the fungus to other animals and people.

Diagnosing Ringworm

Your vet likely will take a hair or skin sample from a lesion and perform a fungal culture to determine if your dog has ringworm. Usually, the results are available within a few days, but sometimes the spores take time to grow. It can take up to a month before your vet can confirm that your dog has ringworm. While a culture is the most accurate way to identify the infection, your vet also might use a Wood's lamp. With this test, the hair sample placed under the lamp glows green if ringworm spores are present. However, not all spores will glow. Certain products used on dogs will glow under the lamp, resulting in a false positive.

Similar Conditions

While you can purchase lime dips and anti-fungal shampoos over the counter to treat ringworm without a definite diagnosis, you could be wasting your time and risking your dog's health. Other conditions with symptoms resembling ringworm include flea or food allergies, mange and certain yeast or bacterial infections. That's why your vet will perform a fungal culture on your dog, even if the lesions look like a textbook case of ringworm