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Ringworm in Canines

Ringworm (dermatophytosis) is a fungal infection that affects humans and animals, including dogs. It is caused by a group of fungi known as dermatophytes, which thrive in warm, moist environments. Ringworm in dogs is highly contagious and can spread to other dogs, pets, and even humans. You should take immediate action and seek veterinary care if you believe your dog may have ringworm.


Ringworm in dogs typically appears as circular, raised, and reddish lesions on the skin. These lesions can be itchy, scaly, and sometimes have a crusty appearance. Hair loss may occur in and around the lesion, giving it a ring-like appearance. The affected area may also be tender to the touch. Please avoid contact with the infected area to prevent getting ringworm yourself.

While ringworm can occur anywhere on a dog's body, it is usually found on the head, ears, paws, and tail. In some cases, many lesions may be present. Ringworm can also infect the nails, causing them to become thickened, brittle, and discolored.


Ringworm in dogs is caused by several different species of fungi. Some examples include:

  • Microsporum canis
  • Trichophyton spp.
  • Microsporum spp.

These fungi live in soil, on surfaces such as carpets, bedding, and grooming tools. They also live on other animals, such as cats and rodents. Dogs with weakened immune systems are more susceptible to developing ringworm. This includes to puppies, senior dogs, and dogs with other underlying health conditions. Dogs that live in crowded, unsanitary conditions also have an increased risk.


A ringworm diagnosis in dogs can be challenging as the symptoms can look the same as other skin issues. Your veterinarian will perform a thorough physical exam and will recommend diagnostics.

Some examples include:

  • Skin cytology: This checks for different types of bacterial and yeast infections. These samples can tested in different ways and can be done in-clinic. The vet might do an impression smear, where they will press a microscope slide to the infected area and then stain it to read under a microscope. They could also take a cotton swap and roll that on the infected area then roll it on to a microscope slide. Another common way is a tape prep. This is where the vet takes a clear piece of tape and presses it onto the infected area. They then put a drop of purple Wright's stain on the slide and then place the tape over it. The stain helps the bacteria and yeast show up easily underneath the microscope.
  • Skin scrape: This helps diagnose demodex and can be done in-clinic. Obtaining this sample is more intrusive than obtaining a sample for a skin cytology. The vet or technician will take sterile scalpel and "scrape" a sample of your dogs skin until they get a good enough sample of skin cells. This may cause some bleeding but do not be alarmed! It will heal easily and you can always ask you vet to apply some antiseptic cream to the area(s).
  • Fungal culture: This involves taking a small sample of hair, skin, or nail from the affected area and placing it on a special culture medium. The sample is then observed for fungal growth over several days, usually about 2 weeks. If ringworm is present, the culture will show characteristic fungal growth patterns. This is typically the gold-standard as far as diagnosing ringworm goes. Make sure to treat your dog per your vet's instructions while you are waiting on results.
  • Ringworm PCR Panel: This involves taking a sample of skin cells from your dog and sending off to a diagnostic lab. This test will look for the 3 common types of ringworm that we discussed earlier. This usually takes about 1-3 business days for results. Idexx is the primary lab that your veterinarian would send this particular panel to. Your vet may change the treatment plan for your dog depending on the results.


Treatment for ringworm in dogs typically involves a combination of topical and oral medications. Topical treatments are applied directly to the affected area to kill the fungi and reduce itching and inflammation. This could include sprays, creams/ointment and antifungal shampoos. Oral medications may also be prescribed to help eliminate the infection. Examples of these include terbinafine, ketoconazole, or itraconazole.

It's important to note that treatment for ringworm in dogs can be lengthy and may need several weeks to even months of medication. Infected dogs may need to be isolated from other animals to prevent the spread of the infection. You also need to be wary of keeping yourself safe and when dealing with and medicating the infected area.


Preventing ringworm in dogs involves taking several precautions to reduce the risk of exposure. These precautions include:

  • Keeping your dog's living environment clean and well-maintained. This will also help keep you from getting infected.
  • Keep your dog will groomed and nails clipped.
  • Monitor their activity outside, especially if they have a weakened immune system.
  • Limiting your dog's exposure to other animals and wildlife that may be infected.
  • Providing your dog with a healthy diet and regular exercise to boost their immune system.
  • Regularly inspecting your dog's skin and coat to make sure they are happy and healthy.
  • Seeking veterinary care at the first sign of any skin issues.

In conclusion, ringworm is a common fungal infection that can affect dogs of any age or breed. Early detection and treatment can help to reduce the risk of spreading the infection to other animals or humans. Pet owners should be aware of the symptoms of ringworm and take steps to keep their dogs healthy and free from infection. Ringworm is a scary term for any pet owner to hear. You always think it can't happen to you until it does! Make sure you rely on and trust your veterinarian to properly treat and care for your pet. Open and honest communication with your dog's healthcare team will ensure a speedy recovery.

If you are concerned about your dog’s skin health, the DIG Labs Health Check can help you monitor through taking photos. Through photos, you’ll receive tips and tricks for better skin health and recommendations on when to go to the veterinarian from the comfort of your home. Try it for free today!