Canine Ringworm Signs, Diagnosis and Treatment

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Canine ringworm is a fungal disease that affects your dog's hair and skin. Regardless of the name, the condition has nothing to do with worms.

Canine Ringworm Is a Common Skin Disorder

Canine ringworm is one of the most common skin disorders for a dog. It is characterized by red, hairless patches on your dog. These patches have pale skin in the center. The name ringworm does not refer to the cause of the problem, but rather to what the patch looks like.


Ringworm is a skin disorder caused by a variety of species of fungus in both animals and humans. The fungi live in the hair follicles of the skin and can be easily transmitted during skin-to-skin contact. In fact, canine ringworm can be transmitted from animal to animal, human to animal and animal to human.

The fungus is spread by spores, and these spores can live for 18 months in bedding or other places where an infected animal has been. Spores can survive on grooming tools as well. If your pet lies down on the infected bedding, the spores can get on him and begin to grow in his hair follicles.

If you have been exposed to an animal with ringworm, you should begin watching your own skin for signs of the disease. It can take about two weeks to develop after the initial exposure.


The most common sign of ringworm on your dog is a round patch of skin where the hair has fallen out. There may be a crusty surface on the skin of the dog. The patch, or lesion, will often start out quite small and then grow. It is most commonly found on the head, but it may also occur on any other area of a dog's body, including the tail. Although the areas are not usually painful, they may cause your dog to scratch.

Occasionally, canine ringworm will not appear in a circle but will instead spread in a patchy way that resembles mange.

How Ringworm Is Diagnosed

Your vet may diagnose canine ringworm in a variety of ways. He will look carefully at the spots and examine your dog thoroughly for fleas and other parasites that might cause the problem. However, the most common method of diagnosing ringworm is by using a tool called a Wood's light. This is much like a black light, a special type of ultraviolet light that causes the fungi to glow. It does not hurt your pet a bit.

Another way that your vet may check for signs of ringworm is to take a sample of your dog's hair to the lab. After a few weeks he can see if the fungus is growing and determine if it is actually canine ringworm.


Once your vet diagnoses your dog with ringworm, he will give you instructions for treating it. How you are instructed to deal with the ringworm will depend on many factors, including:

  • The health of your dog
  • Your lifestyle
  • The vet's preference
  • The severity of the problem

Generally, the vet will prescribe an antifungal shampoo. You will be asked to shampoo your dog with it thoroughly every other day for a week. You will also need to clear out any bedding or brushes that could be harboring the fungus.

You may also be given an antifungal cream to rub on the lesions every day for ten days. If the problem is severe your vet may decide to prescribe an oral medication. This medication is usually given to the dog daily or twice daily for a month. When the condition proves most difficult to control, it may be necessary to shave the dog completely to remove all traces of fungus living in the hair shafts.

Although canine ringworm can often make your pet look very ill, it is not dangerous. With the proper treatment and some precautions, your pet can easily recover from this skin disorder.

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Canine Ringworm Signs, Diagnosis and Treatment