How to Tell If Your Dog Has Ringworm

Updated on July 11, 2019
alexadry profile image

Adrienne is a certified dog trainer, former veterinary assistant, and the author of "Brain Training for Dogs."


How to Tell If Your Dogs Has Ringworm

Hairless patches the size of a quarter may be descriptive enough of ringworm, but not always. There are many skin conditions that may share the same symptoms and this is the main reason why veterinarians have a hard time coming to a diagnosis by looks alone. Also, ringworm does not necessarily always show as round patches and may appear as large hairless areas or irregular shapes and sizes. It's very likely that your vet will take a skin scraping and send it out to a laboratory. Since it may take some time for the results to come in, sometimes veterinarians will prescribe anti-fungal creams right away if ringworm is at the top of their suspicions.

Early Indications

You groom your dog one morning and you find a hairless patch the size of a quarter. Then some time later you find another one and then another one. Concerned about these unsightly spots, you take your dog to the vet for a diagnosis: "Ringworm."

What Is Ringworm?

The first time dog owners hear the word ''ringworm'' they very likely think they are dealing with some sort of parasite. The word is misleading as ringworm is caused by a fungus. There are theories that the word ''ringworm'' may have originated because from the past belief that the patchy circular areas were caused by a worm.

What Is the Ringworm Fungus

The fungus behind the unsightly patches can belong to different families: Microsporum canis (the most common), Microsporumgypseum, and Trichophyton mentagrophytes. This fungus is highly contagious to other dogs, cats, and people, so you will want to keep your dog away from your other dogs and pets, disinfect common areas, and wash your hands thoroughly after handling him.

Dog ringworm fungal skin disorder can come from cats.
Dog ringworm fungal skin disorder can come from cats.


Your dog can get ringworm even from cats!

Using Ultraviolet Light to See Ringworm

Owners may try to find out if their dog has ringworm by using an ultraviolet light or black light. About 50% of ringworm cases will cause the lesion to glow. A bright apple green fluorescence found on the hair shafts may help diagnose the dog. However, if the lesion does not glow consider that it does not necessarily mean the dog does not have ringworm. Many veterinarians will perform this test in their offices.

Has Your Been Exposed to Other Dogs With Ringworm

Another way to tell if your dog has ringworm is if he has been exposed to other dogs with this condition. If your dog has frequented a dog grooming center, a kennel or has been in contact with other dogs or stray cats, then he may have picked up this skin disorder from these places and these animals. Consider that the incubation time, that is the time between when your dog was in contact with the potential cause and the time the first symptoms arise, may be around 10 to 12 days.

Check Your Environment

Consider though that at times dogs can pick up the disease from an infected environment. This means all it it takes is exposure to infected materials such as bedding, carpets, hair clippers, combs and even dirt. Even exposure to other dogs that appear healthy may cause ringworm as some dogs may be carriers of the skin disorder without showing any signs of actual disease.

What to Do If You Expect Your Dog Has Ringworm

If you suspect ringworm in your dog, your best bet is to have your dog see your vet. Your vet can only prescribe the most effective treatment and confirm or rule out this annoying skin condition. Even though ringworm eventually clears up on its own, prescription medications will shorten the course of the disease lessening the amount of time your dog may be contagious.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2010 Adrienne Farricelli


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    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      14 months ago

      Ringworm is generally found in young animals and the hair would be broken off. The round, hairless areas are often the size of coin. A hot spot is oozy of serum and is red and raw and painful.

    • Angie Mayo profile image

      Angie Mayo 

      14 months ago from Victoria Australia

      How can you tell the difference between a ringworm and a hot spot?

    • jandee profile image


      9 years ago from Liverpool.U.K

      Scary ! Lot's of poor stray cats hang around my gate as the man next door feeds them and now I'm worried,jandee

    • bayoulady profile image


      9 years ago from Northern Louisiana,USA

      I 've had dogs all my life. You taught me something.(I thought I knew all about dog's skin issues by now......) I'm lucky I'm following you! I'll make sure to keep my dog Sweetie Pie away from cats with ringworm.Thanks.

    • dallas93444 profile image

      Dallas W Thompson 

      9 years ago from Bakersfield, CA

      Informative hub. Take care of your pet and they take care of you!


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