Ringworm in Dogs: What You Need to Know

8 min read
8 min read

Updated - Aug 29th, 2022

Key Points

  • Ringworm is the common name for a fungal infection that infects almost all species of domesticated animals, as well as humans.
  • These fungal spores can remain dormant on surfaces for up to 18 months.
  • While not life-threatening, ringworm is contagious and requires veterinary intervention.

Many pet parents are surprised to learn that ringworm isn’t a worm at all, but rather a fungal infection of the skin, hair, and nails. The scientific term for ringworm is dermatophytosis, named after the fungi responsible for the infection – a group called dermatophytes.

Unfortunately, ringworm is highly contagious, affecting dogs and cats alike. This fungal infection can be contracted from direct contact with contaminated surfaces or other infected animals or humans. It mainly presents itself as circular patches of hair loss in dogs. These patches can take on a rough appearance as they heal, and can also become inflamed and scab over. Other symptoms include dry, brittle nails, excessive dandruff, and darkened skin patches.

Your vet will diagnose ringworm with either a Wood’s lamp, fungal culture, or PCR test. If the fungal infection is confirmed, treatment will likely consist of quarantine, topical and oral medications, and environmental decontamination.

Symptoms of ringworm

Ringworm will present itself as circular areas of hair loss with red, crusty edges. These hairless patches – also called alopecia – can show up anywhere on your dog’s body but tend to appear on the ears, face, tail, and feet.

As these skin lesions expand, the central area may heal, allowing hair to regrow in the lesion’s center and causing patches to look rough and uneven. The hair shafts that sprout from the lesions break easily, which helps the fungus spread.

While itchiness isn’t normally a symptom in dogs, the affected areas can become inflamed and scabby. The fungus can also spread to your dog’s nails and make them brittle, dry, and rough. Other signs of ringworm include dry, scaly skin, spots of excessive dandruff, changes to your dog’s coat, darkened patches of skin, and inflamed nail beds. 

Dogs can have ringworm infection and show few symptoms, or none at all. Unfortunately, these furry friends are still contagious and can spread the skin infection to other pets and family members.


  • Direct contact with the fungus through another pet or a human
  • Direct contact with contaminated objects or surfaces
  • Contracting the fungus from soil or dirt – especially in warm, humid environments

Pets with weakened immune systems are more likely to contract ringworm. Additionally, skin conditions, open sores, and broken skin make a dog or cat more prone to infection.


Hair loss can be caused by other skin conditions – so it’s important that pet owners consult their veterinarian to verify a diagnosis of ringworm.

The three most common procedures vets use to diagnose ringworm are:

  • Wood’s lamp: This device emits ultraviolet light that can detect Microsporum canis (the fungus responsible for most cases of ringworm in pets) in your dog’s hair follicles. The downside of this test is that it cannot pick up the presence of ringworm if your pet is asymptomatic.
  • Fungal culture: A sample of your dog’s skin, hair, or scab is taken and placed on a culture medium, where it’s allowed to grow. Your vet then observes the culture under a microscope to determine whether ringworm is present. A positive result can show up in 3-5 days, but it can take anywhere from 10-21 days to obtain a result.
  • PCR test: This test looks for the presence of fungal DNA in your dog’s hair and offers the quickest turnaround, with results available in 3-5 days. Because the test cannot differentiate between DNA from living or dead fungi, it’s only effective as a diagnosis of ringworm and not as a follow-up test to see if the fungus has cleared.


Ringworm isn’t life-threatening, but veterinary care is necessary to treat the stubborn fungal infection and prevent it from spreading further. Your dog’s vet will likely prescribe a regimen that includes all or most of the following treatment options:

  • Quarantine: While they’re receiving treatment for ringworm, keep your dog away from other pets and family members. Ideally, the room where they quarantine should be easy to clean and free of wood floors, rugs, and other upholstery.
  • Topical treatments: Lime Sulfur dips and anti-fungal shampoos are the two main topical treatments. Lime Sulfur dips are smelly but tend to be more effective in treating ringworm. Some pet parents opt to have them done at their vet hospital. Medicated creams and ointments have been found to be ineffective against ringworm.
  • Oral medication: Anti-fungal medication taken orally cuts off the dermatophyte’s ability to reproduce and spread. Many vets prescribe oral medication and topical treatments that work together to treat the fungus.
  • Environmental decontamination: To prevent the fungus from spreading to other members of your family (pets and humans alike) quarantine your infected pet throughout treatment and disinfect surfaces, furniture, toys, brushes, combs, etc.– anything that might have come into contact with the fungus.

If aggressively treated, your pup’s ringworm infection should clear in about three weeks. It’s essential to follow your vet’s instructions and complete the entire treatment as stopping treatment prematurely can cause the fungal infection to linger and remain contagious for an extended period of time. Your dog is considered successfully treated once they’ve received two consecutive negative fungal cultures.

Recovery and care

Your canine companion will most likely recover from a ringworm infection within a few weeks if given appropriate medical care, although treatment can sometimes take a few months. Tests to monitor the progression of treatment should be administered every 2-3 weeks until the fungus has cleared.

Remember, some pets can be silent carriers, so be sure to test all other pets in your home if one of them has contracted ringworm.


The best way to prevent ringworm is to keep your space clean! Disinfect surfaces and contaminated objects to remove ringworm spores. Fungal spores can be killed with a mixture of one pint of chlorine bleach in a gallon of water (a 1:4 ratio).

It’s also important to keep your infected dog or cat separate from other pets and family members to prevent the spread of ringworm. Wear gloves when applying medicated shampoo and other topical ointments to prevent reinfection.

What to expect at the vet’s office

So, you’ve made the smart decision to consult your veterinarian about suspected ringworm in your dog. Once you arrive, your vet will conduct a thorough examination of your pet’s coat and skin, possibly using a Wood’s lamp to detect the fungus. They will likely take samples of hair and skin since the most accurate diagnosis of ringworm is from examining a culture of the fungus in a lab.

If your vet suspects ringworm, they will prescribe a treatment plan that includes medication, quarantine, and environmental decontamination. They might also recommend further testing to rule out other skin conditions and possible causes of the lesions.

The bottom line

Though curable, ringworm is contagious and requires diligent treatment to keep it from spreading to other members of your household. You can help keep the fungus contained and eradicate it quickly as possible by following these three steps:

  1. Quarantine your infected pet
  2. Administer treatment per your veterinarian’s instructions
  3. Disinfect your home with particular focus on areas your dog inhabits the most


What is the risk of spreading ringworm to humans?

Ringworm spreads easily to people. Athlete’s foot, jock itch, and scalp ringworm (in children) are common examples of this fungal infection in humans; it can also infect the body and nails.

If you notice skin lesions that are raised and roughly circular with red, scaly edges, contact your doctor. People with compromised immune systems, the elderly, and children are at greater risk of contracting ringworm.

Will my dog recover from a ringworm infection?

If you follow your vet’s treatment plan, your dog will most likely recover from ringworm within a few weeks to a few months. Like humans, dogs with compromised immune systems can contract ringworm more easily and take a longer time to recover.

Can ringworm go away on its own?

When it comes to ringworm, it’s best to seek help asap! While technically ringworm infections can resolve on their own in about 9-12 months, neglecting to consult a vet for treatment will cause the fungus to spread. As a result, more of your dog’s hair may fall out, leaving them prone to wounds and secondary infections. If left untreated, ringworm will almost certainly spread through your house and the surrounding environment, infecting your other family members and pets.

Did you know?

  • Ringworm can be present in soil – especially if many wild animals live near you – so discourage your dog from digging to help keep them ringworm-free.
  • While not usually itchy in dogs, ringworm is often itchy in humans.
  • Terriers – specifically Boston Terriers, Jack Russell Terriers, and Yorkshire Terriers – are more prone to contracting ringworm.
  • Yearly check-ups help keep your pooch healthy and make it easier to spot ringworm and other worm infections that dogs get. In addition to dog insurance plans, Pumpkin offers Preventive Essentials. This is not insurance, but an optional wellness package that refunds 100% of your dog’s annual wellness exam fee. Want to see for yourself? Fetch your free quote today!

Erin McGuff-Pennington

Erin McGuff-Pennington

Erin is a writer and human mom to Rufus, an adorable, sometimes-curmudgeonly Irish terrier who loves peanut butter and is afraid of cats.
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