Can Your Dog or Cat Get Ringworm?

This fungal skin disease is usually associated with humans, but it can affect dogs and cats too. Though unsightly, it can be treated with conventional medication and/or alternative remedies.

Ringworm is a skin disease that has been around for over 5,000 years in humans. But it also occurs in a number of animals, including dogs and cats. This article digs under the surface of this condition to reveal its causes, signs and symptoms, and how it can be treated, both conventionally and holistically.


Despite its name, ringworm is actually a fungus. It also occurs only on the skin, and not in the GI tract like most real worms. There are about 40 types of fungus that can cause ringworm in various species, all belonging to a group called the “dermatophytes”.

A more scientific name for ringworm is dermatophytosis, but you don’t hear that term often. In humans, fungal infections of the skin are also called “tinea”, followed by a name indicating where the infection is (e.g. Tinea corporis for ringworm on the body).

Ringworm looks much the same no matter which fungus is causing it. In fact, this is where the name came from, because in humans, the fungus forms a red ring on the skin with some flakiness inside. Dogs usually have one or more round, crusty areas, while in cats the area is flaky, and can be either round or more irregular in shape. In animal, however, it’s less common to see a ring around the patches.


Ringworm is most commonly seen in young dogs and cats; in stressed or sick animals living in crowded conditions (especially animal shelters); and in animals suffering from an immune deficiency. There is no good way to tell when a kitten or puppy is developing ringworm before it shows up as one or more spots on the skin. So an apparently healthy young animal can develop ringworm soon after being brought home from the shelter.


Ringworm is spread by direct contact with animals or humans who have ringworm, and by contact with ringworm spores from infected hair and dandruff, or anything that comes in contact with those materials (e.g. collars, brushes, clothes, rugs, couches, dirt, dust, etc.). The spores are infectious for a year or longer.

Both dogs and cats, especially longhaired cats, can also be ringworm carriers, which means they don’t show any signs of skin problems but are harboring the fungus on their hair.


Treatment for ringworm is the same no matter which fungus is causing it. Healthy animals can often get rid of an infection in about three weeks without treatment, but they will be shedding infectious material throughout that time. So to prevent the spread of ringworm to people and other animals in the household, it is best to treat the problem as soon as a diagnosis of ringworm is made.

As long as the animal is basically healthy, natural treatments applied to the ringworm spots can work well. If the dog or cat’s immune system is not working well, you may need to use both conventional and natural treatments. Keep in mind that suspected ringworm carriers should also be treated, to help prevent spread of the disease.


Conventional treatment can include oral medication, ointment, and medicated selenium-based shampoo.


  • Vinegar has been used for thousands of years for ringworm, and its effectiveness has been verified by current research. Paint the hairless areas three times a day. You can use a cotton ball or cotton-tipped applicator to apply it.
  • One drop of grapefruit seed extract (not grapeseed extract) in one tablespoonful of water can also be used, applied twice a day.
  • Aloe vera applied to the spot one to three times a day may work, although not as consistently.
  • Other remedies such as crushed garlic, turmeric, or essential oils, mixed with coconut oil or olive oil, can work as topical applications, but they are messy and can stain furniture and rugs. The treated area usually has to be bandaged.


  • When treating a dog or cat infected with ringworm, it’s also important to thoroughly vacuum carpets and furniture, and wash bedding and clothing.
  • Always wear gloves when treating ringworm on your animal, so you do not expose yourself.
  • If the spots have a lot of crustiness or thick flakes, gently scrub as you apply the treatment.
  • You must keep treating ringworm until normal hair starts growing back. This can take up to three weeks or more.


All types are of ringworm are diagnosed the same way. About 50% of cases will fluoresce green under ultraviolet light from a Wood’s lamp. If there is no fluorescence, hairs can be plucked from the area and checked through a microscope for the fungus itself, although it is not always easy to find infected hairs.

Another way to check for ringworm is to scrape off flakes or parts of the crust and culture them to see if one of the fungi grows. It can take up to two weeks for growth to occur. Some labs can also do a faster PCR test to test for ringworm DNA, if crusts or flakes are sent to them for analysis.


In dogs, and cats, ringworm is usually caused by a fungus called Microsporum canis. “Canis” means “dog”, but about 98% of cases in cats are caused by M. canis compared to 70% of cases in dogs. The second most common cause of ringworm in dogs is Microsporum gypseum, while about 10% of cases in dogs arise from Trichophyton mentagrophytes. T. mentagrophytes is also the second-most common cause of ringworm in humans, and can cause the disease in cats as well.

If you suspect your dog or cat may have ringworm, take him to the vet for a diagnosis before it spreads to the rest of your human and animal family. Properly treated, it should clear up within a month.

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