Ringworm in dogs appears as circular patches of hair loss with a crusty, scaly coating, most commonly on the face, ears, paws, and forelegs. It is not caused by a worm. It is a fungal skin infection called dermatophytosis. Approximately 70% of dog ringworm cases are caused by the fungus Microsporum canis, according to the Merck Veterinary Manual.
For related reading, see Cushing's Syndrome in Dogs: Back Leg Weakness, Hair Loss, and Comparison With Diabetes.
What Does Ringworm Look Like on a Dog?
For veterinary context, see this reliable source.
Ringworm on a dog looks like one or more round bald patches where the hair has broken off at the skin line. The patches may have a crusty or scaly covering. The edge of the lesion is often raised, red, or inflamed, while the center may begin to clear and look normal as the lesion grows outward.
There are 4 main visual presentations of ringworm on dogs:
- Circular bald patch with grey, scaly skin: The most common appearance. The patch is dry, flaky, and covered in fine white or grey scales resembling dandruff.
- Round patch with a red, raised edge: The outer ring is inflamed and red. The center appears less active. This is the appearance most people associate with the name "ringworm."
- Crusty bald spot with broken hairs: Short, stubble-like broken hairs surround the edge of the lesion. The skin beneath looks thickened and darkened.
- Acne-like bumps alongside hair loss: In some dogs, small raised bumps appear alongside the bald area, particularly on the muzzle or face.
In rare cases, infected dogs show no visible signs at all. These asymptomatic carriers can still spread the infection to other animals and humans.
Where Does Ringworm Appear on a Dog?
Ringworm most commonly appears on a dog's face, ear tips, tail, paws, and forelegs. The fungus targets the hair follicles and upper skin layer, so areas with thinner or shorter coat coverage show visible lesions earliest. Ringworm can appear anywhere on the body and, in severe or untreated cases, spreads across the entire coat.
The most affected body areas, in order of frequency:
- Muzzle and face
- Ear tips and edges
- Forepaws and legs
- Underbelly
- Tail base
- Nail beds (causing brittle, rough claws)
What Do Ringworm Patches Feel Like?
Ringworm patches feel dry, rough, and scaly to the touch. The skin at the lesion site is often thickened. Unlike hot spots, ringworm lesions are not wet or moist. The hair in and around the patch is brittle and breaks off easily, which is the primary way the infection spreads through a household.
Ringworm usually does not cause intense itching. This is one of the key differences between ringworm and mange. A dog with ringworm may occasionally lick or groom the lesion, but it will not scratch frantically the way a dog with sarcoptic mange does.
What Does Ringworm Look Like vs. Mange vs. a Bald Spot?
Several skin conditions in dogs look similar to ringworm. The table below compares the 3 most commonly confused conditions.
| Feature | Ringworm | Sarcoptic Mange | Demodectic Mange |
|---|---|---|---|
| Cause | Fungus (M. canis, M. gypseum) | Sarcoptic mites | Demodex mites |
| Appearance | Round bald patches, crusty edges, scaly skin | Red, crusty skin with small red dots or bumps | Bald patches, thinning coat, scabbing |
| Itching | Usually mild or absent | Intense; dogs scratch until skin breaks | Mild unless secondary infection develops |
| Shape | Circular, defined edges | Irregular; spreads widely | Irregular; can be localised or generalised |
| Contagious | Yes — to other pets and people | Yes — to other pets; limited to humans | No |
| Common locations | Face, ears, paws, forelegs | Ears, face, legs, armpits | Face, paws, trunk |
| Skin texture | Dry, scaly, flaky | Red, bald, crusty | Thinning, sometimes greasy |
How Is Ringworm Different from a Regular Bald Spot?
A bald spot caused by ringworm has a circular or near-circular shape with a defined or raised edge. Bald spots caused by other conditions, such as hypothyroidism, Cushing's disease, or nutrient deficiency, tend to be more diffuse, symmetrical, and spread across larger areas of the body without localised crusty edges. Hot spots are moist, red, and often smell strongly. Ringworm lesions are dry.
How Is Ringworm Different from Mange?
The key distinguishing feature is itching intensity and lesion texture:
- Mange causes intense, relentless scratching. Dogs with sarcoptic mange often scratch and bite at themselves until the skin bleeds.
- Ringworm usually causes little to no itching. The dog may leave the lesion alone entirely.
- Mange lesions spread rapidly over large areas of the body. Ringworm starts in discrete circular patches.
- Mange lesions are redder, angrier, and accompanied by small red dots or pustules. Ringworm lesions are dry and scaly.
Both conditions require veterinary diagnosis. They cannot be reliably distinguished at home because early-stage presentations can overlap significantly.
Why Is My Dog Losing Hair in Patches?
A dog losing hair in patches has 4 main possible causes: ringworm, mange, bacterial skin infection (folliculitis), or hormonal or systemic disease. Ringworm is confirmed only by a positive fungal culture, Wood's lamp examination, or microscopic hair sample analysis. A veterinary examination is required to rule out other conditions.
Other causes of patchy hair loss in dogs include:
- Hypothyroidism: Hair loss is bilateral and symmetrical, often across the trunk and flanks, without skin inflammation
- Cushing's disease (hyperadrenocorticism): Hair loss across the body, pot-bellied appearance, increased thirst and urination
- Nutrient imbalance: Generalised dull coat and diffuse shedding, not circular patches
- Allergies: Diffuse redness, itching, and hair loss, often involving paws and belly, without circular crusty lesions
- Folliculitis (bacterial infection): Pus-filled bumps, redness, and patchy hair loss, often with odour
According to the American Kennel Club, hair loss combined with changes in coat appearance or inflamed skin may also indicate serious underlying conditions. A veterinarian should examine any unexplained bald spot that persists for more than 1 week.
Who Is Most at Risk of Getting Ringworm?
Dogs most at risk of ringworm infection include those in 4 high-risk categories:
- Puppies under 1 year old: Immature immune systems make young dogs the most susceptible. Puppies in kennels or shelters are particularly vulnerable.
- Elderly dogs: Aging immune systems are less effective at fighting off fungal spores.
- Long-haired breeds: Breeds such as Yorkshire Terriers are noted in the Merck Veterinary Manual as prone to persistent and widespread ringworm infection.
- Immunocompromised dogs: Dogs on long-term corticosteroids or with underlying diseases have reduced ability to resist dermatophyte infections.
The incubation period for ringworm is 10 to 12 days. Symptoms appear approximately 10 to 12 days after exposure to an infected animal or contaminated surface. Ringworm spores survive in the environment for 6 weeks to 18 months, making environmental decontamination a critical part of treatment.
Is Ringworm in Dogs Contagious to Humans?
Ringworm is zoonotic, meaning it can spread from dogs to humans. The fungi responsible, primarily Microsporum canis, Microsporum gypseum, and Trichophyton mentagrophytes, infect both animals and people. In humans, ringworm produces the classic ring-shaped red rash with raised edges. Children are particularly susceptible and should avoid direct contact with a dog diagnosed with ringworm until treatment is completed.
Ringworm spreads through 3 routes:
- Direct contact with an infected dog's skin or coat
- Contact with contaminated objects, including bedding, grooming tools, furniture, and carpets
- Broken hairs carrying spores shed into the environment
How Is Ringworm in Dogs Diagnosed?
A veterinarian uses 3 diagnostic methods to confirm ringworm:
- Wood's lamp examination: A special UV light that causes certain strains of Microsporum canis to fluoresce apple-green. Not all ringworm strains fluoresce, so this test alone is not definitive.
- Microscopic hair examination: Hair samples from the lesion edge are examined under a microscope for fungal spores on the hair shaft. This allows early diagnosis.
- Fungal culture: Hair and skin scrapings are cultured in a laboratory medium. This is the most accurate diagnostic method. Results take 10 days to 2 weeks.
A vet may also examine your dog for the characteristic circular patches of hair loss, redness, crusting, and scaling as part of a physical examination. Because ringworm resembles mange, allergies, and bacterial infections, laboratory confirmation is essential before treatment begins.
How Is Ringworm in Dogs Treated?
Ringworm in dogs is treated using 3 simultaneous approaches:
- Topical antifungal therapy: Antifungal shampoo, cream, or ointment applied to the affected areas. Long-haired dogs are clipped around lesions to improve medication contact. Topical treatment controls environmental contamination by reducing shedding of spores.
- Oral antifungal medication: Systemic antifungal drugs are prescribed for a minimum of 6 weeks, sometimes longer. Treatment must not stop until a veterinarian confirms 2 consecutive negative fungal cultures.
- Environmental decontamination: All bedding, grooming tools, and surfaces the dog contacts are cleaned with diluted bleach. Ringworm spores are hardy and persist in carpets, furniture, and flooring for months.
Treatment duration ranges from a few weeks to several months, depending on the severity of the infection, the dog's immune response, and how consistently treatment is followed. Stopping treatment early because lesions appear to clear is the most common cause of recurrence.
When to See a Vet for a Dog with Hair Loss
See a vet immediately if your dog shows any of the following:
- Circular bald patches with crusty or scaly edges
- Multiple patches of hair loss appearing within days of each other
- Bald spots on the face, ears, or paws with no obvious cause
- Hair loss accompanied by redness, thickening, or darkened skin
- Any human in the household develops a red circular rash after the dog's symptoms appeared
- The bald spot has not resolved within 1 week
Ringworm does not resolve reliably without treatment. The Merck Veterinary Manual notes that while ringworm infections in healthy adult dogs can occasionally self-resolve, treatment speeds recovery and prevents spread to other animals and people in the household.
Helen L. Corlew runs a team of Samoyeds, Alaskan malamutes and Alaskan huskies. I am a Tellington TTouch practitioner and use this mode of work with training and living with my dogs.
Helen Corlew founded Prairie Isle Dog Trekking in Petersburg, North Dakota in 2010, and has spent the fifteen years since doing something most people only read about: teaching real dog sledding on real prairie terrain, at the edge of a landscape that doesn’t apologize for being difficult.
She is not a weekend enthusiast. She harnesses working dogs in January cold, trains handlers who have never touched a sled, and has built one of the only hands-on mushing education programs on the Northern Great Plains — from a single address on Highway 2, with no marketing budget and no shortcuts.
Her writing on Prairie Isle Dog Trekking reflects the same philosophy. Whether she is covering trail safety across the Rockies, breed behavior in extreme conditions, or what it actually takes to trek with a dog in the Alps, Helen writes from the position of someone who has done the work before writing the sentence.
She lives and runs dogs in Nelson County, North Dakota.
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