Dog Ringworm Signs & Symptoms

Written by jacqueline lerche
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Dog Ringworm Signs & Symptoms
Puppies and dogs with compromised immune systems are susceptible to ringworm. (Puppy eyes image by Marfa Faber from

Ringworm is an irritating skin infection caused by a fungus. Dogs contract ringworm from other dogs, cats or rodents or from digging and rolling in infected soil, according to the University of Illinois College of Veterinary Medicine. Veterinarians diagnose ringworm by removing a few affected hairs from the dog and allowing the fungus to grow. The veterinarian will identify the growing fungus under a microscope. Ringworm treatment involves anti-fungal medication, medicated shampoos and dips, and hair removal.

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Early Signs

Dogs with ringworm have rings or circular patches of bare, irritated skin that can appear anywhere on the dog's body. Multiple, intersecting patches of infected skin may give the condition an irregular shape, according to Iowa State University College of Veterinary Medicine. The hair surrounding the infected skin breaks off at the surface and appears shaven. In the early stages of the condition, the skin on the outer edge of the bald patch is swollen and red. The inner section appears pale and flaky. Pustules and boils may develop.

Signs of Advanced Ringworm

The outer ring, or lesion, becomes increasingly swollen and crusty as the infection progresses. Some dogs may have a kerion reaction where a portion of infected skin becomes thickened, extremely inflamed and fills with pus. In rare cases, persistent scratching of infected skin may cause the fungus to infect the dog's claws and cause abnormal growth.

Behavioural Changes

Dogs infected with ringworm will scratch and chew the affected skin. Painful inflammation may cause dogs to be sensitive or cautious about being touched.


Some dogs are carriers of ringworm and show no signs or symptoms of the condition. These dogs can infect other pets in the same household. Cats and rabbits may also be carriers of ringworm, according to the University of South Florida. Grooming tools used on several pets may be a means of spreading the fungus to other pets.


Clinical signs of ringworm appear between two to four weeks of exposure. The fungus will concentrate on areas of the dog's coat after seven days.


Ringworm is often over-diagnosed in dogs, according to the University of Minnesota College of Veterinary Medicine. The condition appears most frequently in puppies and adult dogs with compromised immune systems. Kidney disease, liver disease and cancer are conditions which compromise immune function.

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