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Ringworm in Dogs 

Unlike viral and bacterial infections, like rabies and distemper, fungal infections, like ringworm, aren’t as well-known and can be more difficult to prevent. If your pet shows symptoms of ringworm, doing your research and consulting your veterinarian is essential.

What is ringworm in dogs? 

Ringworm—also known as dermatophytosis—is a fungal infection that commonly affects the skin, hair and nails. Some symptoms of ringworm in dogs are easy to spot due to the raised, red rings it can cause on your pet’s skin. Contrary to its name, however, ringworm lesions aren’t always round and it doesn’t involve actual worms.

Ringworm in dogs is caused by a group of fungi called dermatophytes. The most common ringworm-causing species are Trichophyton mentagrophytes, Microsporum canis and Microsporum gypseum. All three species cause the same symptoms.

While typically not severe, ringworm in dogs and humans is very contagious and can cause significant discomfort for your pup. Always seek out veterinary services if you suspect your dog has ringworm.

How do dogs get ringworm? 

Ringworm in dogs—and humans—is transmitted when the fungus or fungal spores come in contact with the skin. It’s more likely to cause an infection if broken skin is present—such as a rash or laceration.

Contamination can occur in a few different ways. Your dog may come in contact with another animal or human that has ringworm—even those showing no symptoms—or with contaminated objects like grooming tools or bedding. They can also get ringworm from digging or rolling in dirt containing spores, which is why it is common to see ringworm in dogs’ paws.

A higher amount of fungus in an environment can make this infection more likely to occur. It’s more common in warmer climates and in environments with lots of canines—like boarding kennels and shelters.

Dogs with weaker immune systems—including puppies, seniors and those with certain medical conditions—are more susceptible to ringworm. Hunting or working dogs may also be more likely to get ringworm as they work outside and are more frequently exposed to dirt and fungal spores.

How do I prevent ringworm? 

Maintaining skin health is one of the best ways to prevent ringworm in dogs. Regular checkups allow your veterinarian to spot signs of skin or immune conditions that may increase the risk of ringworm. A Petco Vital Care plan provides unlimited routine exams at in–network vets that can help ensure your pup’s wellness. Vitamins and supplements for the skin may also be recommended, and good nutrition is essential.

 If your dog spends a lot of time outside, you can also use a medicated, antifungal shampoo on their body and paws once or twice a week to help prevent ringworm. Because ringworm in dogs’ eyes is also a risk, ensure you keep your indoor environment clean of any dirt by vacuuming regularly. Always treat any wounds and keep them sanitized.

Ringworm is not a death sentence, but it is a serious condition that requires intensive treatment. If you suspect your dog has ringworm, see your veterinarian as soon as possible to get them back on the road to healing.  

What are the symptoms of ringworm in dogs? 

The symptoms of ringworm in dogs include patchy or circular hair loss, dandruff, red or dark-colored skin and crusty or scab-like marks. It can also sometimes cause raised abscesses called kerions. Dogs with ringworm don’t always feel itchy. If your dog shows any signs of ringworm, you should always consult your veterinarian even if your pup isn’t scratching.

Ringworm symptoms most commonly occur and are most noticeable on a dog’s face and ears. Ringworm in dogs’ paws and tails is also common but may be harder to spot.  

Dogs can also be silent carriers of ringworm. This means they host the fungus that causes ringworm but don’t show any symptoms. However, they can still pass it on to other animals and humans. Always test any other animals or humans your dog has been in contact with if they’re diagnosed with ringworm.

How is ringworm diagnosed? 

The stages of ringworm in dogs are diagnosed in several ways. A Wood’s lamp can be used to shine fluorescent light on infected hairs and obtain a rapid result. However, not all ringworm-causing fungi can be seen under the light, which can result in a false negative.

Your veterinarian will use a follow-up method to confirm the diagnosis. The most reliable technique is collection of a fungal culture followed by a lab analysis. This method can be slow, however, as spores may take up to a month to grow. For a quicker diagnosis of ringworm in dogs, your vet may take a skin scraping and examine it under a microscope.

If your dog is positive for ringworm, other animals and people in your home should also be tested if they show symptoms.

What are the stages of ringworm in dogs?  

If your dog is exposed to enough fungus to cause ringworm, you’ll typically start to notice the telltale rings in about 7 to 14 days—although it can take up to 21 days. It’s easy to mistake the early symptoms of ringworm in dogs for allergies or even a small cut, as the spots may look like pimples or scabs.

As ringworm progresses, the small spots will evolve into more extensive areas of hair loss, lesions and red or scaly skin. As they continue to grow, they may turn into scabs or begin to heal in the middle while still appearing raw around the edges.

Once you start treatment, the spots may continue to grow temporarily. Within about two weeks, they should shrink and the hair will begin to grow back—although it may be discolored at first. However, severe ringworm in dogs can cause bacterial infections that severely damage hair follicles and prevent regrowth.

Is ringworm in dogs contagious? 

Yes, ringworm is highly contagious. Each of the most common fungi that cause ringworm in dogs are zoonotic,meaning they can be passed to other domesticated animals and humans. If you suspect or know that your dog has ringworm, wear gloves while handling them and always wash your hands immediately after contact.

How long does ringworm last in dogs? 

When properly treated, the symptoms of ringworm in dogs last a few weeks—although infections of the nail bed can take a few months to clear up entirely. Your pup will also be contagious for about three weeks. It’s crucial to follow your veterinarian’s treatment plan exactly, as stopping treatment too soon or skipping medication doses will cause ringworm to last longer.

Without treatment, there’s no set recovery time for dogs with ringworm. It can spread over the entire body and last for months, or even indefinitely, and they will remain contagious and extremely uncomfortable throughout that time. While ringworm is not deadly to dogs, it can result in secondary infections that can cause even more problems.

How do I cure ringworm in dogs? 

The cure for ringworm in dogs depends on the severity of the infection. Mild cases can usually be treated with topical medications, while severe cases may require oral prescriptions from the pharmacy.    

Common topical creams for ringworm in dogs include miconazole and clotrimazole, which are usually applied for two to four weeks. If your pet has long fur, their coat may need to be shaved to help the medication absorb. Topical treatments can also include shampoos, rinses and dips.

Oral medications include antifungal drugs like griseofulvin, itraconazole or terbinafine. You may need to administer these for several months, even if it appears the symptoms have subsided.

Your veterinarian will likely take skin cultures periodically during treatment to determine if your dog is cured. Once your pup has two negative cultures in a row, you can discontinue treatment. Until then, follow your veterinarian’s instructions exactly. If you stop too soon, ringworm can recur and your dog can become contagious again.

Ringworm in dogs is more common if there is an underlying skin condition or disorder. Along with ringworm, you may also need to treat allergies and food sensitivities as well as immune disorders or malnutrition issues.

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Reviewed by Dr. Whitney Miller, DVM, MBA, DACVPM

As Petco’s Chief Veterinarian, Dr. Miller is the lead veterinary subject matter expert, overseeing the company’s standards of excellence in animal care and welfare, growth in pet services and much more. Dr. Miller leads Petco’s medical team, supporting over 200 full-service hospitals and mobile vaccination clinics operating in over 1,000 Petco Pet Care Centers nationwide