If you have noticed a round, bare patch on your dog’s coat, ringworm is one of the first things a veterinarian will want to rule out. Despite the name, ringworm is not a worm at all. It is a fungal infection of the skin, hair, and sometimes claws, known medically as dermatophytosis. In dogs, about 70 percent of cases are caused by the fungus Microsporum canis, with most of the rest coming from Microsporum gypseum found in soil or Trichophyton mentagrophytes carried by rodents. The fungi feed on keratin, the protein in hair and skin, and produce hardy spores that can survive on brushes, bedding, and furniture for up to 18 months. Ringworm is also zoonotic, which means it can spread from pets to people, so early recognition and treatment protect the whole household.
Symptoms of Ringworm in Dogs
- Circular or irregular patches of hair loss, often with scaly or crusty skin
- Broken, brittle hairs around the edges of the patch
- Mild redness or scabbing, though many lesions are not itchy at all
- Lesions most often on the face, ear tips, paws, tail, and belly
- Rough, brittle, or misshapen claws in rare cases
Some dogs carry the fungus without showing any lesions. These silent carriers can still spread spores to other animals and to people, which is why diagnosis matters even for dogs that look healthy after exposure. Puppies, seniors, and breeds such as Yorkshire Terriers tend to develop more persistent, widespread infections.
When to See a Vet
Contact your veterinarian whenever you find a patch of hair loss that grows over days, especially if it looks circular with a healing center. Seek help sooner if more than one patch appears, if other pets or family members develop similar ring-shaped skin lesions, or if your dog is scratching the area raw. A veterinary visit is also wise after known exposure to an infected animal, even before symptoms begin, because early treatment limits environmental contamination.
Common Vet-Directed Treatments
Vets combine several diagnostic tools because no single test is perfect. A Wood’s lamp makes some strains glow yellow-green under ultraviolet light, fungal culture of plucked hairs is the most accurate method, and PCR testing offers faster results. Once ringworm is confirmed, treatment usually pairs topical therapy with oral medication for anything beyond a small patch.
- Topical antifungal creams or ointments such as miconazole, clotrimazole, or terbinafine on localized lesions
- Medicated baths with a chlorhexidine and miconazole shampoo, or a lime sulfur dip given twice weekly to treat the whole coat and reduce spore shedding
- Oral antifungals such as itraconazole or terbinafine for multifocal or stubborn infections, often continued for six to eight weeks or longer
Your vet will repeat fungal cultures during treatment and confirm the cure with negative results. Stopping medication as soon as the hair grows back is the most common reason ringworm returns, so follow the full prescribed course.
Home Care
Because spores linger in the environment, home cleaning is half the battle. Confine the infected dog to one easy-to-clean room, vacuum floors and furniture daily, and discard the bag or empty the canister outside. Wash bedding, towels, and soft toys in hot water, and disinfect bowls, crates, and grooming tools with a diluted bleach solution. Wear gloves when applying dips or creams, keep children away from the treated areas, and handle other pets last so you do not carry spores between them.
Prevention
Prevention focuses on limiting exposure and catching lesions early. Quarantine new pets until they have a clean health check, avoid sharing brushes or bedding between animals, and groom your dog regularly so bare patches are noticed quickly. During an active infection, separating the affected dog from other pets and treating every animal your vet recommends will shorten the outbreak for the whole household.
Disclaimer: This article is for educational content only and is not a substitute for professional veterinary advice. Always consult a licensed veterinarian for diagnosis and treatment of your pet.