What Is Ringworm in Dogs? Next Steps Explained

Updated December 28, 2021
vet apply ointment on dogs nose to treat ringworm

Canine ringworm is a fungal disease that can affect your dog's hair and skin. Regardless of the name, the condition has nothing to do with worms. If you've been told that your dog has ringworm or worry that they may be suffering from this skin disorder, it's important to understand exactly what this means and how to proceed.

What Is Ringworm in Dogs?

Canine ringworm, also referred to as dermatophytosis, is a very common skin disorder in dogs. It is caused by direct contact with a fungus, which can be a number of different species but is most commonly Microsporum canis, as it accounts for 70 percent of all ringworm cases in dogs.

The fungal spores are highly contagious and can spread to other animals and even humans. This condition is characterized by red, hairless patches that can appear anywhere on the body. The name "ringworm" does not refer to the cause of the problem, but rather to what these patches look like, because true ringworm lesions closely resemble a red ring.

Signs and Symptoms

The most recognizable sign of ringworm in dogs is a round patch of hair loss with a sometimes scaley appearance on the skin. The patch, or lesion, will often start out quite small and then grow. Other signs of a ringworm infection include:

  • Dull fur
  • Alopecia (hair loss)
  • Broken hairs
  • Itching
  • Crusty, round lesions
  • Red skin
  • Dandruff
  • Brittle or broken nails

Unfortunately, some dogs can carry ringworm without displaying any symptoms at all. These are known as "asymptomatic carriers," although it's more common to see cats as asymptomatic carriers compared to dogs. These individuals are usually not identified until several other pets or people in the house continuously become reinfected with ringworm. Asymptomatic carriers are particularly problematic in high-traffic areas, such as shelters or boarding facilities.

Where Is Ringworm Found on Dogs?

Ringworm lesions can occur any part of the body, but there are some areas that are most commonly affected.

  • Face and snout
  • Ears (usually the ear tips)
  • Tail
  • Feet

How Ringworm Spreads

The ringworm fungus is spread by spores, and these spores can live for 18 months in bedding, soil, or other places where an infected animal has been. If your pet lies down on infected bedding, the spores can get on them and may begin to grow in their hair follicles. Ringworm can survive on grooming tools, as well.

The fungi live in the hair follicles of the skin and can be easily transmitted during skin-to-skin contact. In fact, canine ringworm can be transmitted from animal to animal, human to animal, and animal to human. If you have been exposed to a pet with ringworm, you should begin watching your own skin for signs of the disease. It can take anywhere from four to 14 days for you to develop symptoms after the initial exposure.

However, exposure to ringworm doesn't always mean that a dog will become infected. If they have a strong immune system and healthy skin, the fungus may not thrive. However, if a dog is fighting off a hidden infection or has compromised skin, they can easily catch ringworm. Infected dogs will likely show signs within two to three weeks of exposure.

Dogs at High Risk for Ringworm

Any dog can become infected with ringworm after exposure to the spores, but some dogs are at higher risk. Puppies and senior dogs tend to be most commonly affected. Dogs with compromised immune systems due to disease or who are on medications like steroids or immunosuppressant drugs have difficulty fighting off infections. Those with allergies are at higher risk, as well.

Dr. Anthea Schick, DVM, DACVD, a veterinary dermatologist, reports that certain breeds may be more prone to ringworm than others. These include Russell Terriers, Yorkshire Terriers, and Boston Terriers.

Diagnosing Canine Ringworm

Veterinarian exploring a dogs skin with a wood lamp

Your veterinarian may use various methods to diagnose canine ringworm.

  • Visual examination: They will look carefully at the spots to visually determine if the areas look suspicious for ringworm, or symptoms indicate another skin condition. Many of the signs of ringworm, such hair loss, itchy spots, and crusting, could point to a few different skin problems.
  • Wood's lamp: The most common method of diagnosing ringworm is by using a tool called a Wood's lamp or light. This is a very non-invasive technique, although it's not always definitive. The Wood's lamp is much like a black light. It casts a special type of ultraviolet light that can cause fungi to fluoresce or glow.
  • Microscopic exam: Your veterinarian may look at a few plucked hairs or skin cells under a microscope. This will allow them to visualize the hair follicle in detail and identify the fungus.
  • Fungal culture: Culturing the fungus is the most reliable diagnostic method, but it does take several days to get results. Your vet will pluck several hairs from the suspicious area and send them to an outside laboratory where they will plate the cells in a special medium and monitor it for growth.
  • Biopsy: In rare cases, usually if the area is not responding to multiple treatments, your vet may send out a biopsy of the skin.

Treatment Options

dog getting bath to treat ringworm

How your vet chooses to treat the ringworm will depend on many factors, including the health of your dog, your lifestyle, and the severity of the infection. Even "minor" cases must be treated to prevent spreading or reinfection.

  • Topical ointment: Generally, you'll be prescribed an antifungal cream to apply to your dog's lesions every day for a few weeks to months. You'll need to keep a cone on your pup to prevent them from licking the cream off, as it can be harmful if ingested.
  • Oral anti-fungal medication: If the problem is severe or there are several lesions over your dog's body, your vet may decide to prescribe an oral medication. This medicine is usually given once or twice daily for six weeks or as directed.
  • Medicated dips or baths: For pets who have numerous lesions on the body or severe infections, a lime sulfur dip or medicated shampoo may be recommended. These are often done at the veterinary hospital, but you may be instructed to bathe your pet at home. If you do this, be sure to wear protective apparel to prevent spreading the fungus.

Tips to Prevent Ringworm Infections

Even if your pet doesn't fall into the high-risk category, it's wise to know how to reduce the chances of your dog contracting ringworm.

  • Keep your dog's skin healthy with a nutritious, balanced diet.
  • Avoid letting them come in contact with infected animals.
  • Decontaminate your environment if anyone in the household has had ringworm within the last 18 months. Thoroughly vacuum all carpets and furniture and wash bedding, toys, leashes, etc.
  • Before bringing home a new kitten, puppy, or any pet from a multi-animal environment like a shelter, look out for signs of ringworm and have them examined by a veterinarian.

One Ringworm to Rule Them All

Although canine ringworm can often make your pet uncomfortable, it is not life-threatening. With proper treatment and precautions to protect yourself, your pet can easily recover from this skin disorder.

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What Is Ringworm in Dogs? Next Steps Explained