How to tell if your dog has ringworm—and what you can do

January 13, 2024 - 5 min read

The information in this article has been reviewed by Dr. Jennifer Coates, DVM on January 12, 2024 . Although it may provide helpful guidance, it should not be substituted for professional veterinary advice.

Dog with ringworm on his nose

Despite its name, the common canine illness known as “ringworm” isn't caused by a worm at all. Actually, it's a fungal infection that affects your pup's skin, hair, and nails.

Read on to learn what ringworm in dogs looks like, how it spreads, and what you can do to prevent and treat it.

What is ringworm in dogs?

Unlike heartworm (which is very much an actual worm), ringworm is an infection caused by “dermatophytes,” a type of fungus.

It’s called ringworm because it often presents as a circular patch on people’s skin, but this is not always the case in dogs. Dermatophytes thrive on keratin, a protein found in skin, hair, and nails, which is why the infection tends to affect these areas.

There are several types of dermatophytes that can cause ringworm in dogs. The most common are “Microsporum canis,” “Microsporum gypseum,” and “Trichophyton mentagrophytes.”(Interesting fact: Even though “Microsporum canis” essentially means “small spores of the dog,” it’s even more likely to afflict cats.)

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Each type of fungus has a slightly different way of spreading and affecting your dog, but the overall symptoms and treatments are similar across the board.

How do dogs get ringworm?

Small happy dog portrait, close-up of cute brown puppy smiling outdoors in a park, funny emotional puppy with tongue sticking out

Ringworm is highly contagious, and dogs can contract the condition in a few different ways. Direct contact with an infected animal is one possible method of transmission. This can include interactions with other dogs, interactions with cats, or even interactions with wildlife carrying the fungus.

And this contact doesn't necessarily have to be aggressive, like biting or scratching. It can be as simple as touching or rubbing against the infected area where the fungus is present. Ringworm fungi live in the skin and hair, so any contact with these infected areas can spread the infection.

Dogs can also pick up ringworm from environments or objects contaminated with the fungus. This includes places like dog parks, kennels, or grooming salons, as well as personal items like bedding, brushes, and toys. And unfortunately, the fungus can survive for a long time on these surfaces, just waiting for a host to brush by.

Soil is another possible (though less common) source of infection. Certain types of ringworm fungi live in the soil, and dogs digging or playing in contaminated soil may contract the infection.

Understanding these transmission pathways can help you take appropriate preventative steps to keep your furry friend ringworm-free.

Symptoms of ringworm in dogs

small chocolate labrador retriever puppy combats itching by scratching with its hind leg

Ringworm in dogs sometimes presents as circular, bald patches that may appear red and scaly. These patches often start small but can spread over time. They may have a ring-like appearance, hence the name of the disease.

How to tell if your dog has ringworm

The appearance of ringworm can vary, and it might not always present as a distinct ring-shaped patch.

In some instances, the infection can cause irregularly shaped patches rather than round ones. And the central area may start to heal, making the ring less apparent. Plus, thick fur can hide ringworm lesions, making them less noticeable.

So it’s important to look out for other symptoms as well, including:

  • Scaly, crusted skin: The affected area might be flaky and crusted, accompanied by inflammation.

  • Thin hair: Hair may be broken or sparser than normal, even if the affected area isn’t completely bald.

  • Itching and discomfort: Some dogs may itch and scratch at the affected areas, though this is not always the case.

  • Nail and claw infections: Ringworm fungi love keratin, so the illness can cause your dog’s nails to become brittle or misshapen.

  • More unusual symptoms: Ringworm can sometimes cause infections under or deep within the skin, leading to nodules, ulcers, and drainage.

It's important to note that ringworm symptoms can vary widely. Some dogs may show only mild signs, while others can come down with obviously severe infections. Just keep in mind that the former can turn into the latter faster than you’d think, so early detection is extremely important.

If you notice any of these symptoms in your dog, it’s wise to consult with a veterinarian as soon as possible. Early diagnosis and treatment can help prevent the spread of the infection.

How is ringworm diagnosed?

A nervous Jack Russell is calmed by a female veterinarian in an animal hospital prior to a surgical procedure.

When it comes to diagnosing ringworm in dogs, veterinarians typically start with a physical examination, looking closely at the symptoms presented. Laboratory tests are necessary for a definitive diagnosis, however.

Here are some common diagnostic techniques:

  • Fungal culture: This is the most definitive test. Samples of hair or skin cells are taken and cultured to identify the specific fungus causing the infection.

  • Wood's lamp examination: A special UV light is used to identify certain types of ringworm fungi that fluoresce under the light. However, not all ringworm species glow, and false-positive results are possible too, so additional testing is often necessary.

  • Microscopic examination: Sometimes a microscope is used to examine hairs or skin scrapings for signs of the fungus.

How is ringworm treated?

Close up image of dog's nose ringworm treatment. Applying cream on ringworm lesions.

Once diagnosed, the treatment for ringworm in dogs generally involves a combination of topical therapies and oral medications.

Topical treatments for ringworm include medicated shampoos, dips, ointments, or creams. In most cases, the dog’s entire body should be treated, not just the obviously affected areas. Topical medications help to reduce the spread of the fungus and soothe the skin.

Oral antifungal medications are prescribed to more completely treat the infection and are essential for eliminating the fungus from the body.

Your veterinarian will also recommend methods for decontaminating your dog’s environment, which may include vacuuming, laundering, and disinfecting.

The treatment duration can vary, often lasting several weeks to make sure the infection is completely eradicated. Pet parents should closely follow their vet’s instructions; premature discontinuation of treatment can lead to a recurrence.

How to prevent ringworm

Dog taking a bubble bath in grooming salon

Want to prevent your pup from contracting ringworm in the first place? It’s mostly about keeping your dog’s skin and immune system as healthy as possible, plus supervising your dog’s interactions with other animals (and humans). Fortunately, healthy adult dogs are actually quite resistant to ringworm infections but become more susceptible if they’re suffering from skin damage or health problems that weaken the immune system.

Ringworm prevention is one of many reasons why you should regularly groom your dog and clean their living spaces. Bathing your pup with a pet-safe shampoo and keeping their coat well-groomed reduces the risk of fungal infections and lets you pick up on any skin problems as early as possible. And regularly sanitizing bedding, toys, and floors can help eliminate any lingering fungal spores.

If you have multiple pets and one of them contracts ringworm, keep them in a separate room or area away from other pets and family members. Make sure this area is easy to clean, be sure to disinfect it regularly, and limit direct contact with your pet until they’ve been treated and cleared by a vet. Isolating your infected pet can help prevent its spread to other animals or even to humans. 

That last part is worth reiterating: humans can indeed contract ringworm, and dogs can spread it to us. Practice good hygiene by washing your hands thoroughly and changing your clothes after handling your infected dog or cleaning their living areas.

And, of course, you should strictly adhere to the treatment regimen prescribed by your vet, including both topical and oral medications. Regular vet check-ups are important to monitor the progress of the treatment and make any necessary adjustments.

When to see a vet for your dog's ringworm

Husky dog being inspected by vet

If you notice any of the common symptoms of ringworm, like circular patches of hair loss, scaly skin, hair loss, or changes in your dog’s nails, it's always wise to schedule a vet visit. Prompt veterinary attention not only aids in early diagnosis but also prevents the spread of the infection to other pets and people.

If your dog is already being treated for ringworm but their symptoms are persisting or worsening, a follow-up vet visit is necessary. Your dog may need a different treatment approach, or your vet may need to diagnose and address a different underlying health issue that’s complicating their recovery. 

In moments like these, dog insurance can be a lifesaver, helping you seek needed vet care without draining your finances. It's one small step that can make a big difference in managing your pet’s health needs, whether they suffer from ringworm or any other condition.

David Teich
Lead Editor

David oversees content strategy and development at ManyPets. As Lead Editor, he focuses on delivering accurate information related to pet care and insurance. David’s editorial background spans more than a decade, including a pivotal role at Digiday, where he wrote content and managed relationships with media and tech companies. As an Associate Editor at Cynopsis Media, David wrote the Cynopsis Digital newsletter and interviewed executives and digital marketing experts in the TV industry. His background also includes film journalism. His diverse experiences in journalism and marketing underpins his role in shaping content within the pet care industry.