This article was updated on September 19th, 2023
Even though the name suggests it, ringworm is actually not a worm or a parasite. Instead, it’s a fungal infection that can make a ring-looking lesion on your pup’s skin.
However, a ring shape is just one of many presentations that you may see with a ringworm infection. Since it’s contagious to humans and other animals, it’s important to know what you’re looking for when you suspect that your dog may have ringworm.
What exactly is ringworm?
Despite being named after a worm, ringworm is actually caused by a fungus. The infection results in hair loss and scaly patches of skin. The lesions are typically circular, but they are not always in a “ring” presentation. The very outer ring is often scaly. It is an infection that can spread quickly and even pass to humans (Zoonotic).
Usually ringworm isn’t itchy, but you may notice your dog licking the hairless area. You could also see redness and inflammation of the skin that can cause itching and secondary infections.
Ringworm often starts out as a spot of hair loss that may later turn red throughout the lesion or along the edges. You can click here to see a picture of a severe case of ringworm on a dog’s face (Picture: © Ian Brett Spiegel VMD, MHS, DACVD).
What does ringworm look like on dogs?
Key characteristics of ringworm lesions in dogs include:
- Hair loss often in a circular pattern
- A skin lesion with red, scaly edges
- Broken or brittle hair
- Lots of dandruff
- Brittle or misshapen nails
- Red, inflamed, or dark nail beds
Ringworm can show up anywhere on a dog’s body but is more commonly found on the face, ears, tail, and feet, especially around the toenails.
Pictures of ringworm lesions (with veterinarian explanations)
Here’s a look at different presentations of ringworm in dogs:
Here is a circular area of hair loss with a crusty, scaly center. The edges of the lesion are redder and more inflamed than the center.
This ringworm lesion is more inflamed overall, perhaps due to the dog licking it. If left untreated, the size of the spot may increase in size or become infected due to the dog licking it.
The edges of this ringworm lesion are very inflamed. As the infection progresses, the center of the area of hair loss may start to heal and even regrow hair.
Pictured below is a dog with ringworm: you can see several clearly demarcated areas where the fur is thinner and the skin is flaky and crusty (the lesions were present mostly around the dog’s armpits, belly/groin, legs and nose.)
How do I know if my dog really has ringworm?
One of the most common ways that dog owners diagnose ringworm is when it spreads from their dog to them or their other pets. But for a definitive diagnosis, you’ll need to get your veterinarian involved. There are a few different ways that your vet will determine if your dog has ringworm or some other skin condition.
1. Wood’s Lamp
The Wood’s Lamp is a great first-step option to try when a vet suspects ringworm. This is a special ultraviolet light that is shined on the dog’s lesions. Nearly ¾ of ringworm infections will fluoresce green under this special light.
If a hairless patch doesn’t glow green, that doesn’t mean that it’s not ringworm. There are still the other 25% of ringworm infections to account for that won’t glow. The type of ringworm and the length of time a dog has had the lesion can all account for why ringworm won’t glow.
If a lesion doesn’t glow under the Wood’s Lamp, the next step may be to do a fungal culture. The vet will collect skin scrapings from the scales and edges of the lesion as well as some hair and attempt to grow the fungus on a culture medium. This test can take as little as 3 days or as long as 21 days for a result.
On the newer side of ringworm diagnosis is PCR testing. This test is run using hair collected near the lesion. It looks for the presence of fungal DNA and will have results in 3-5 days. This test can produce some false positives, so a culture may be run at the same time if there is any question.
Disclaimer: This content is not a substitute for veterinary care. Always consult with your vet for health decisions. Learn more.
Veterinarian’s Tip: Ringworm is contagious to both humans and other animals!
What looks like ringworm – but is not ringworm?
As with all common skin infections, there can be some that look similar to each other. Ringworm is no different. Skin infections, allergic reactions, and hot spots can all take on the look of ringworm. Let’s look at some of the differences you may notice.
Both of these skin lesions have incomplete hair loss, meaning that the hair has thinned but isn’t totally gone in the lesion. They are also very flaky and crusty, which could mean that they are moist and oozing instead of dry and scaly.
This hot spot is very inflamed, and no doubt causes the dog a lot of discomfort. It is very moist and may start to develop a foul odor. View more pictures of hot spots with veterinarian descriptions and advice.
Treatment for ringworm
Ringworm is a fungal disease, so it should be treated with antifungals. Antifungals won’t treat allergies or bacterial infections, so it’s important that you get a proper diagnosis before trying anything at home.
That being said, you’ll find many products labeled for curing ringworm that range from shampoos to sprays and ointments. Never use any products without veterinary supervision, as some of them may actually be harmful to your pup.
What you can do at home is try to keep your dog separate from other pets to prevent the spread and wash your hands after petting them. Try to confine them to a room or two in your house that is easy to clean.
All of the little hairs that your dog sheds every day could potentially be infected with fungal spores, so you’ll need to vacuum, sweep, or mop all surfaces to cut down on transmission. Using a dilute bleach solution can also help disinfect hard surfaces.
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Veterinary Treatment for Ringworm
Depending on how bad your dog’s ringworm is, your vet may prescribe topical or oral antifungals, or both. Dogs with one or two lesions may get by with a medicated shampoo or ointment, while multiple lesions may require the addition of an oral medication.
Keep in mind that it takes a long time to clear a ringworm infection: potentially 4-8 weeks or longer, even with treatment. Generally speaking, the more aggressive the treatment, the less time a dog remains contagious. Your pup will need a recheck culture to make sure all of the fungal spores are gone before stopping treatment.
While treating ringworm may require a lengthy time commitment, it’s fortunately not very expensive to treat. Most dogs will cost under $100 for diagnosis and treatment. Of course, this price will increase if the infection persists and requires more medication or more in-depth diagnostics.
What should I do if my dog does have ringworm?
If you notice any new lesions on your dog’s skin, it’s best to see your veterinarian. This is especially important when you suspect ringworm so that you can better prevent it from spreading to other pets or people. Keep your pup separated from others and in an easy-to-clean room.
Use any prescriptions exactly as they are prescribed at the proper dosage and length of time to keep the infection from coming back and to help cut down on the amount of time that your dog stays contagious.
How fast will my dog recover?
Ringworm is not a quick cure, no matter how aggressive the treatment is. It just takes time to kill the fungus and heal the lesion. Expect your dog to remain contagious for at least three weeks with proper treatment (more without treatment) and not to expect a cure for 4-8 weeks or more.
Veterinarian Tip: Make sure to keep your pet with ringworm isolated and always wash your hands after touching them, until your vet says they are no longer contagious.