By Dial A Vet Veterinary Team
Ringworm is not a worm. It is a fungal infection of the skin, hair and nails, and it is one of the few common pet skin problems that spreads easily to people, particularly children. Its spores can survive in a home for a year or more. Many round, hairless patches on dogs turn out to be something else, such as a bacterial skin infection, so it is worth confirming before you scrub the house from top to bottom. If anyone in the family develops an itchy, ring-shaped rash, they should see their GP.
Key takeaways
- Ringworm (dermatophytosis) is a fungal infection caused mainly by Microsporum canis, Nannizzia gypsea and Trichophyton species.
- It spreads by direct contact with infected animals or people, and by spores on bedding, brushes and furniture.
- It is zoonotic. People with a suspicious rash should see a GP.
- A vet needs to confirm the diagnosis, as other skin conditions look very similar.
- Treatment usually combines vet-prescribed treatment for the dog with thorough cleaning of the home.
How dogs catch ringworm
- Microsporum canis: mostly spread from cats, especially kittens, and from other dogs.
- Nannizzia gypsea (previously Microsporum gypseum): lives in soil. Dogs that dig are more exposed.
- Trichophyton species: often picked up from rodents, hedgehogs or their burrows, common in hunting and terrier breeds.
Puppies, older dogs, dogs with other illnesses, and dogs living in crowded settings such as shelters are most at risk. Healthy adult dogs often have a degree of natural resistance.
Signs of ringworm in dogs
- Round or irregular patches of hair loss, often on the face, ears, paws and legs
- Scaly, flaky or crusty skin within the patch
- Broken hairs or stubble around the edges
- Redness, sometimes with a raised, inflamed lump (kerion)
- Mild to moderate itch, though many dogs are not itchy
- Rough, brittle or misshapen nails in some cases
The classic "ring" with a healing centre is less obvious in dogs than in people.
Conditions that look similar
Bacterial skin infection (pyoderma), demodectic mange, allergies, hot spots and some immune skin diseases can all cause round hairless patches. This is why a diagnosis matters. See hot spots on dogs for one common lookalike.
When to see a vet
Ringworm itself is not an emergency.
Same day or next day: patches that are spreading quickly, oozing or painful, a puppy with multiple lesions, or a dog that seems unwell.
Book a visit soon: any patch of hair loss you are unsure about, particularly if there are young children, elderly or immunocompromised people, or other pets in the home.
What to do now
- Limit close contact, such as sleeping on beds and couches, until your vet confirms the cause.
- Wash your hands after touching your dog, and supervise children.
- Keep your dog's bedding, brushes and collars separate, and do not share grooming tools.
- Check other pets, especially cats and kittens, for patches of hair loss.
- Do not apply tea tree oil, vinegar or other home remedies. They do not reliably treat ringworm and can irritate the skin.
- Anyone with a red, scaly or ring-shaped rash should see their GP and mention the pet.
How vets diagnose ringworm
- Wood's lamp: an ultraviolet light that makes some Microsporum canis infections glow apple green. Many cases do not glow, so a negative result does not rule it out.
- Microscopic hair examination: looks for fungal spores on plucked hairs.
- Fungal culture: hairs and scale are grown in the lab to identify the species. This can take up to two to three weeks.
- PCR testing: detects fungal DNA quickly and is often used alongside culture.
How vets treat ringworm
Treatment is usually a combination of topical therapy, such as medicated washes or rinses, and in many cases a prescription oral antifungal. Clipping very long coats may be suggested. Treatment continues until follow-up tests are negative, not just until the skin looks better, because dogs can still carry spores after the patches heal. Your vet will set the plan and recheck schedule.
Cleaning the home
- Vacuum floors and furniture often and dispose of the contents in a sealed bag.
- Wash bedding, blankets and soft toys in hot water, ideally twice.
- Wipe hard surfaces to remove hair, then use a disinfectant your vet recommends. Diluted household bleach is effective on suitable hard surfaces once they are cleaned.
- Clean grooming tools, collars, crates and car seats.
- Repeat cleaning regularly until your vet confirms your dog is clear.
FAQ
Can ringworm go away on its own?
In some healthy dogs it can resolve over months, but treatment shortens the illness and reduces spread to people and pets.
Can my cat catch it from my dog?
Yes. Cats, especially long-haired cats and kittens, are very susceptible and may carry it without obvious signs.
How long is my dog contagious?
Until treatment has cleared the infection, which your vet confirms with follow-up testing. This often takes several weeks.
Can my dog go to daycare?
Not until your vet says the infection is under control.
Talk with a vet
If you have spotted a patch you are not sure about, a Dial A Vet video consult can help you decide on next steps and what to do at home in the meantime. A dog that is very unwell or in pain should be seen at an in-person clinic, or an emergency vet out of hours.
References
- Moriello KA, et al. Diagnosis and treatment of dermatophytosis in dogs and cats: clinical consensus guidelines of the World Association for Veterinary Dermatology. Veterinary Dermatology, 2017
- Merck Veterinary Manual: Dermatophytosis in Animals
- Healthdirect Australia: Ringworm (tinea)
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. People with skin rashes should see their own doctor.
