By Dial A Vet Veterinary Team
Ringworm sounds like a parasite. It is actually a dermatophyte fungal infection of hair and surface skin. Dogs, cats and people can share some species, which is why households with itchy circular bald patches need a proper diagnosis. Puppies, long-haired breeds and animals under stress are over-represented. Early veterinary care shortens shedding into the environment.
Key takeaways
- Look for circular or patchy hair loss, broken hairs, scale and sometimes itch.
- Cats in the home may carry fungus with subtle signs, so multi-pet checks matter.
- Diagnosis may use Wood's lamp, microscopy and fungal culture or PCR.
- Cleaning bedding and hair in the environment reduces reinfection.
- Related: I think my dog has ringworm, dog skin diseases, dog skin allergies.
What causes ringworm
Common fungi include Microsporum canis (often linked with cats), Microsporum gypseum (soil) and Trichophyton species. Spores cling to hairs and survive in the environment for months under the right conditions. Infection follows contact with an infected animal, contaminated grooming tools, or soil. Shelters and breeding homes may see outbreaks when many young animals share space.
Signs in dogs
- Round patches of hair loss with scaly edges
- Broken stubbly hairs
- Redness, crusts or follicular bumps
- Claw fold inflammation in some cases
- Mild to moderate itch (variable)
- Rarely, more widespread dermatitis in immunosuppressed dogs
Not every circular bald spot is ringworm. Demodex, bacterial infection and allergies can look similar, which is why guessing with human antifungal cream is a poor plan. Photos help remote triage but still need confirmation.
Spread to people and other pets
Household members may develop red, itchy, ring-shaped rashes, especially on arms and faces after cuddling. Children and people with reduced immunity are more susceptible. Wear gloves when applying treatments, wash hands, and ask your GP about human lesions. Treat or screen in-contact cats and dogs as your vet advises. Do not share brushes between pets during an outbreak.
When to see a vet
Book promptly for expanding bald patches, multiple pets affected, or skin disease in a puppy. Urgent care is rarely needed for classic mild ringworm, but secondary deep infections, fever or extreme lethargy should not wait. If a person in the home is severely immunocompromised, tell your vet so isolation advice can be stricter.
How vets diagnose it
A Wood's lamp may cause some Microsporum canis strains to fluoresce apple-green, but a negative lamp does not rule ringworm out. Microscopic examination of plucked hairs and fungal culture or PCR provide stronger evidence. Cultures can take days to weeks. Your vet may start management based on strong clinical suspicion while awaiting results.
Treatment overview
Therapy often combines topical care and, in many cases, systemic antifungal medication prescribed by the veterinarian. Clipping long hair around lesions can help topical contact. Treatment continues until tests show clearance, not merely until hair starts to regrow. Stopping early is a common reason for relapse. Never use tea tree oil as antifungal therapy. Keep Elizabethan collars on if your dog licks topical products off.
Home cleaning
- Wash bedding, collars and toys that tolerate hot washes.
- Vacuum thoroughly and dispose of vacuum contents.
- Discard or disinfect grooming tools as advised.
- Limit the dog to easily cleaned rooms during heavy shedding phases if practical.
- Wear gloves for lesion handling and wash hands afterward.
- Mop hard floors with cleaners your vet or a dermatology reference considers appropriate for spores.
Aftercare and follow-up
Your vet will set recheck timing based on culture or PCR results and clinical progress. Keep other pets separated if advised until clearance. Tell groomers and boarding facilities about the diagnosis before bookings. Patience matters: fungal spores do not vanish overnight even when the dog looks better.
FAQ
Can my dog go to daycare during treatment?
Ask both your vet and the facility. Many pause group care until the dog is no longer considered infectious.
Is ringworm the same as a hot spot?
No. Hot spots are usually surface bacterial infections. They can look wet and painful rather than classic scaly rings. See hot spots on dogs.
Do I need to throw out the sofa?
Usually thorough cleaning is enough. Follow your vet's environmental advice rather than discarding everything immediately.
How long until hair grows back?
Hair regrowth lags behind fungal cure. Expect weeks, and complete the full treatment course.
Talk with a vet
If you see circular hair loss on your dog, or people at home have matching rashes, a Dial A Vet veterinarian can help you plan testing and household steps. Book a Dial A Vet consult.
References
- Merck Veterinary Manual. Dermatophytosis in Dogs and Cats.
- WSAVA / veterinary dermatology consensus material on dermatophyte diagnosis and treatment.
- RSPCA Australia. Ringworm information for pet owners.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If you are worried about your pet right now, contact your local vet or nearest emergency animal hospital.