Ringworm in Dogs: How to Spot, Treat, and Prevent

Written by Alan Lemus
Updated: July 3, 2023
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You are the one who knows your pet the best. Maybe one day while cuddling your furry pet, you may notice something different. Patches in his fur, or maybe he’s itching more and more. While this may be your dog suffering from allergies due to his food, it could also potentially be ringworm. It is good to know how to identify ringworm so you can get it treated right away.

What Is Ringworm?

Ringworm is a fungal infection that affects the hair, skin, and nails of almost all domesticated animals and humans. Despite its misleading name, Ringworm is not actually caused by a worm, unlike tapeworms, hookworms, roundworms, and whipworms. Ringworm is highly contagious and is a zoonotic infection, which indicates it can be passed from an animal to a human. This fungal infection can be found all over the world but thrives in hot climates.

The medical term for ringworm is dermatophytosis, and this is because the fungi that cause the infection are called dermatophytes. Dermatophytes come in a variety of different species. Some dermatophytes are species-specific, meaning they exclusively infect one type of animal, but others may transmit between various animal species or from animals to humans. Microsporum canis, Microsporum gypsum, and Trichophyton mentagrophytes are the three most prevalent fungi that cause ringworm in dogs. Ringworm produces infective spores, which are widespread in the environment. Just one spore can cause this fungal infection, however, only a dog with broken skin can be infected. If your dog has healthy skin, ringworm should not be an issue.

As ringworm is a very common and zoonotic disease, it is very important to be able to recognize, prevent and treat this infection. Certain breeds and categories of dogs are more susceptible to contracting ringworm, so continue reading this article for more information.

How To Recognize Ringworm

Symptoms may take up to three weeks to appear once your dog has been infected. Ringworm usually appears as a red or gray patchy ‘ring’ on the superficial layer (the outer layer) of the skin, hence its name. In the early stages of infection, the sores will appear more irregularly shaped rather than a ring. This ring will have patchy hair or no hair at all and dry skin, as ringworm feeds off the keratin in hair follicles. As these scabby rings become larger, the hair in the center of the ring may grow back. Your dog’s nails also contain keratin, and if they are affected they will appear brittle and weak, with red, inflamed nail beds. 

Skin inflammation and irritation are other very common symptoms of ringworm. Keep an eye out for excess dandruff and dark patches. Although ringworm does not cause itching, you may see your dog scratching more often but this is due to the irritation.


Ringworm in dogs appears as a red or gray patchy ‘ring’ on the top layer of the skin.


How To Diagnose And Treat Ringworm

If you have noticed some of these symptoms in your dog, call the vet straight away and express your concern as this infection needs to be stopped to prevent it from being transmitted to humans or other animals. Your vet will carry out a physical exam as well as a diagnostic exam. This will involve taking a sample of your dog’s hair and skin and examining it under a microscope, looking for the fungus. Another way of diagnosing ringworm is by using an ultraviolet light called a Wood’s lamp to examine your dog’s skin as the fungus may show up under this lighting. The most reliable way of detecting ringworm is by taking a sample of your dog’s skin and hair, placing it in a dish, and leaving it in certain optimal conditions for 10 days. If the fungus grows, ringworm is present.

wood lamp being used on dog

A Wood’s lamp is a UV lamp that can be used to check a dog for ringworm

©GaiBru Photo/Shutterstock.com

There are many different ways to treat ringworm in your dog, and which method of treatment your veterinarian chooses will depend on the type of ringworm and its severity. 

Topical therapy 

Topical therapy is when medication or a cream is applied directly to the skin. Your vet will prescribe an antifungal cream or ointment to apply to localized areas of your pet’s body. Sometimes it is advised to shave the hair surrounding the infected area, and also bathe your dog twice a week with an antifungal shampoo. Always remember to thoroughly wash your hands after treating and bathing your infected dog. Topical medication will last several weeks to several months, and can sometimes be prescribed along with an oral medication. While your dog is being treated, it is essential to provide him/her with a nutrient-rich diet full of minerals and vitamins.

Oral antifungal medication

Oral antifungal medication is a reliable way of treating ringworm. Itraconazole, terbinafine, and griseofulvin are the three most common medications prescribed. If administering oral medication to your dog is challenging, it may help to hide it in their food. Some dogs may experience some side effects such as loss of appetite, diarrhea, and vomiting, but these side effects vary from dog to dog. If your dog is experiencing these side effects quite seriously, consult your vet, but do not take your dog off the medication until instructed to. This oral medication will have to be administered for 6 weeks or more for it to work, and once the treatment is finished, your vet will carry out two consecutive tests for ringworm and both must be negative. Make sure to handle this medication with gloves, and beware that some medications should not be handled if you are pregnant.

dog being given medication

Itraconazole, terbinafine, and griseofulvin are the three most common medications prescribed to treat ringworm in dogs.


If you have more than one pet at home, try to isolate the infected animal to prevent the disease from spreading. Provide him/her with their own room and a clean bed. Your dog will remain contagious for the first three weeks of treatment, and during the remaining time, they will still have the disease but are no longer contagious. Continuously clean and vacuum your home, to remove any spores or infected hair follicles. Chlorine bleach diluted with water can kill ringworm spores. This is especially important to do once your dog tests negative to prevent them from contracting the fungus again. Ensure your pet’s bed and feeding bowl are cleaned daily.

How To Prevent Ringworm In Your Pet

Good hygiene is the best preventative against ringworm. This includes frequent washing of your dog’s bed, toys, bowls, blankets, collars, and any other items they are in contact with frequently. Bathing your animal with an antifungal shampoo is also very beneficial and this will kill any spores.

It is important to know that certain breeds and categories of dogs are more susceptible to ringworm. Older dogs, puppies, and dogs who may have issues with their immune system are more likely to transmit the disease. Breeds such as hunting dogs, Jack Russel, Yorkshire, and Boston Terriers are known to be diagnosed with ringworm often. If your own one of these breeds or categories of dogs, it is important to pay close attention to any symptoms. If your dog is friends with a cat, this can also be an issue as ringworm in cats can also be transmitted to your dog, so this is something you should keep an eye on.

yorkshire dog

Yorkshires, Jack Russells, and Boston Terriers are susceptible to ringworm.

©Anna Vasiljeva/Shutterstock.com

Is Ringworm Dangerous To Humans?

Ringworm is a zoonotic disease which means it can be passed from an animal to a human, or vice versa. You must have broken skin to contract ringworm, which means a scratch, cut, or skin condition such as eczema. Ringworm rarely causes serious issues in humans, the symptoms and preventatives are the same as those of animals. The most common symptom is a mild rash. A person with a compromised immune system, such as someone with Multiple Sclerosis or HIV/AIDs, may find it difficult to get rid of the disease and must take extra caution. It is important to restrict contact with other people if you have ringworm, as well as the use of public spaces as you may contaminate. Ringworm in humans remains contagious for 48 hours, so visit your doctor to be properly treated and to get a sick letter if you need time off work or school.

Knowing how to spot ringworm is very important, not only for your dog’s health but for the health of others too. Ringworm is a disease that can be easily contained and controlled if spotted and treated on time. You know your pet the best so if you notice any changes in your dog’s behavior now you know how to tell if it can be ringworm.

The photo featured at the top of this post is © Nathalie Marran/Shutterstock.com

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About the Author

Alan is a freelance writer and an avid traveler. He specializes in travel content. When he visits home he enjoys spending time with his family Rottie, Opie.

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