Ringworm in Dogs: What It Looks Like, Treatment and Is It Contagious?

What Ringworm Looks Like on Dogs

• Roughly circular patches of hair loss, sometimes with hair regrowing in the center as the patch spreads²
• Dry, gray, scaly or crusted skin, sometimes with redness or small bumps^12,3,4
• Fragile hairs that break off easily^2,3
• Patches often on the face, ear tips, tail and feet³
• Often little or no itching, although this varies^2,4

Lesions usually appear 1 to 3 weeks after exposure, often as dry, gray, scaly patches, and there may be several scattered over the body.^12,2 In dogs, ringworm doesn't always form the neat ring seen in people and can look like many other skin problems.^12,4 Some dogs carry the fungus with no signs and can still spread it.²

Which Dogs Get Ringworm?

Puppies, dogs that roam, hunt or dig, and dogs in warm, humid climates are most at risk. Stress, crowding (for example in shelters or hoarding situations) and other illnesses increase the risk. Yorkshire Terriers are more prone to infection and harder to treat.^4,12,3,6

How Ringworm Spreads

Ringworm spreads by direct contact with an infected animal or person, and through contaminated brushes, bedding, collars and furniture.^2,1 Spores can stay infectious in the home for many months, with commonly cited estimates of up to 18 months.^2,12 Spores don't multiply in the environment, though, and usually need slightly damaged skin to cause infection, so thorough cleaning is effective.^4,5

Can People Catch Ringworm From Dogs?

Yes. In people, ringworm causes a red, itchy, ring-shaped rash that may be scaly inside. On the scalp, it can cause a scaly bald patch, which is more common in children. Symptoms usually appear 4 to 14 days after contact.^9,8 Children, older adults, pregnant women and people with weakened immune systems are at higher risk.^8,12 Serious complications in people are very rare, and the infection is treatable.⁵

• Wear gloves when handling or treating your dog, and wash your hands afterward.^2,1
• Keep your dog in easy-to-clean rooms during treatment.^2,8
• If anyone in the home has ringworm, have all pets checked.⁸

How Vets Diagnose Ringworm

No single test is perfect, so vets usually combine several:^6,5

• Wood's lamp: a UV light that makes most M. canis infections glow apple-green. Other ringworm fungi don't glow, so a negative result doesn't rule it out.^4,5,2
• Microscope exam of hairs for fungal spores.^4,6
• Fungal culture: hairs and scale brushed onto a special medium. It is the most accurate test but can take up to 3 weeks.^2,4
• PCR testing: faster and identifies the fungus, but it can detect dead fungus too, so a positive result doesn't always mean active infection.^5,2
• Biopsy for lumps or unusual lesions such as kerions.^4,7

Treatment

• Whole-body topical treatment, such as a medicated antifungal shampoo or lime sulfur rinse prescribed by your vet, usually twice a week. Spot creams alone aren't enough.^5,12,4
• Oral antifungal medicine for widespread, severe or persistent infections.^5,4
• Clipping affected areas, or the whole coat in widespread cases, with clippers rather than scissors.^2,6

Treatment usually takes 6 to 12 weeks, sometimes longer.^4,2 Your vet will want one or more negative fungal tests, not just healed-looking skin, before stopping. Stopping when the skin only looks better, or using creams alone, are common reasons ringworm comes back.^2,5,12 With treatment, dogs are usually much less contagious after about 3 weeks.²

Cleaning Your Home

Cleaning once or twice a week until your dog is cured helps stop reinfection and protects people and other pets:^4,13

• Remove hair and debris first by vacuuming, sweeping or using lint rollers, then wash surfaces with detergent. Disinfectant doesn't work on dirty surfaces.^4,13,10
• Disinfect hard surfaces with regular household bleach diluted 1:100 (about 2.5 tablespoons per gallon of water), left wet for about 10 minutes, or a disinfectant labeled for Trichophyton. Never mix bleach with other cleaners.^13,10,6
• Wash bedding and fabrics twice on the longest cycle without overloading. Hot water and bleach aren't essential.^11,4
• Carpets: vacuuming alone doesn't remove all spores; shampoo twice or use hot-water extraction.¹⁴
• Throw away items that can't be washed, such as fabric collars, and empty vacuum bags often.¹³

Ringworm vs Hot Spots and Mange

• Hot spots are red, moist, oozing and painful, appear within hours to a day, and are usually caused by licking or scratching. Ringworm patches are usually dry, scaly and slower to develop.^15,2 See hot spots on dogs.
• Demodectic mange and bacterial skin infections can also cause round patches of hair loss and crusts, and bacterial infections are likely more common in dogs than ringworm.^6,16 See mange in dogs.

Because so many conditions look alike, a vet exam and testing are the best way to know.^8,6

Frequently Asked Questions

How do you tell if a dog has ringworm?

Look for round, scaly patches of hair loss with broken hairs. Your vet can screen with a UV lamp and confirm it with a fungal culture or PCR test.

Can I touch my dog if he has ringworm?

Yes, but wear gloves when possible and wash your hands afterward. Keep young children and anyone with a weakened immune system from close contact until your vet says your dog is no longer contagious.

Will ringworm go away on its own in dogs?

Healthy dogs may clear it within weeks to months, but they stay contagious, so treatment is recommended.

How long is a dog contagious with ringworm?

With aggressive treatment, usually about 3 weeks. Without treatment, it can last for months.

What kills ringworm on surfaces?

Cleaning off hair and dirt, then bleach diluted 1:100 or a disinfectant labeled for ringworm fungi.

Can I treat ringworm without a vet?

Spot creams alone usually don't cure it in dogs. A vet can confirm the diagnosis and prescribe effective treatment.