Pet InfoRx®
Cat Ringworm Infection

Ringworm sounds scary but don’t panic because there are no worms involved! It is a treatable infection that is completely manageable.

This pet information prescription will help you know what ringworm is, what to look for, how to treat it, and how to prevent this from happening in the future.


Warning & Precautions

Ringworm is zoonotic, which means it can pass from animals to people and from people to animals. Because ringworm is zoonotic, children and immunocompromised individuals are at an increased risk. They, therefore, should not handle animals that are knowingly infected.

Most adults with a healthy immune system are generally resistant to the infection. Children can acquire infection from pets as well as other children and the outdoors. 

Any human who develops skin lesions should seek medical attention immediately. This is especially important for children, the elderly, or anyone with a compromised immune system (i.e., people on chemotherapy), as they may suffer more discomfort from the lesions. 

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Your Kitty Could Glow!

cat scratching behind ear

Not all 'fungi' are fun! While there are approximately 40 different species of dermatophyte fungi, the bulk of the cases of infections in cats is due to Microsporum Canis (M. Canis). These fungi can be fluorescent under a UV-A light (also known as blacklight from a Wood’s lamp). The area will appear an apple-green color. The unfortunate thing is only about 50% of the M. Canis infections will fluoresce. None of the other dermatophyte infections will fluoresce. But to complicate matters further, certain medications or contaminants on the hair and skin will cause fluorescence, as well. Therefore, a diagnosis of ringworm cannot be made with just a Wood’s lamp. Bloodwork and a skin crape analysis are often needed.

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What Is Ringworm?

Ringworm is a misleading term because a worm does not cause the infection. The actual cause is a fungus that feeds on the protein of the outer layer of hair, nails, and skin. The fungi belong to a specialized group known as dermatophytes. Therefore, the true medical term for ringworm is dermatophytosis. This common skin infection gets its nickname ‘ringworm’ because it causes a circular, red, raised rash – shaped like a ring. 

For cats, it is the most common cause of scaling (dandruff). The signs and symptoms vary a lot. Cats can experience minor or significant hair-loss, scaling, redness, and itching. Younger cat lesions tend to be more inflammatory because their immature immune system doesn't know how to respond. When the lesions first begin, they can be on the face and muzzle, ears, chest, and front legs. The lesions tend to spread quickly to other parts of the body because of self-grooming and coming into contact with infected objects (beds, brushes, etc.).

Feline ringworm can mimic other diseases. Some of these include flea allergic dermatitis, chronic conjunctivitis, miliary dermatitis, etc.

The highly contagious fungus can live on skin, surfaces, soil, and other items such as clothing, brushes, towels, and bedding. Infection occurs in all domesticated species (dogs, cats, horsed, goats, pigs, sheep, etc.) and humans. If there is contact with the fungus, infection does not always occur. If infection is going to occur, it is usually between seven and fourteen days after contact. Animals remain contagious for about 3 weeks even when aggressive treatment occurs. The factors that affect whether infection occurs are the amount of contamination in the environment, the age of the cat, as well the strength of the cat's immune system.

The good news is that most ringworm infections are usually self-limiting. In other words, the infection will resolve on its own without treatment. However, treatment plans help eliminate the infection sooner and help prevent the spread of the infection to other animals and people. Normally, oral anti-fungal medications are not needed, and generally, topical treatments (creams, ointments, or shampoos) are all that is required. However, there are cases where both are needed.

It is estimated that about 20% of cats are carriers. A carrier is a cat that transmits ringworm to the environment and/or animals and people while showing no signs of infection. 

How Did This Happen?

Ringworm is contagious. So, your cat could've gotten an infection by having direct contact with an infected animal or person. Infection can also result from coming into contact with objects, surfaces, or soil that has been contaminated with the fungus.

The fungal spore can live in the environment for up to 18 months. This includes brushes, combs, bedding, furniture, carpets, and other surfaces, like soil. 

two cats outside one has ringworm

What You Should Do If Your Cat Has Ringworm

If you suspect that your cat has ringworm, contacting your veterinarian is important. They will need to perform an exam and obtain samples for a culture to confirm your cat has ringworm.

The chosen treatment plan is based on the following:

  • The severity of the infection
  • The number of pets infected
  • The age and immune status of those in your home. This includes not only animals but people too.

Localized Infection

If the infected area is very small or only on one to two locations, some veterinarians may recommend clipping the affected area(s) to prevent spreading infected fur into the environment and just applying an antifungal cream or ointment to the location. Owners should wear gloves when handling their cats and applying treatments. Treatment should be continued for one to two weeks after all lesions are gone.

Generalized Infection

For larger areas of infections, full-body clips may be recommended as well as antifungal shampoos (only use those recommended by your cat’s veterinarian). You will need to bathe your cat 2 to 3 times per week, and be sure to leave the lather on for fifteen minutes before rinsing in lukewarm water. As a precaution, wearing gloves to bathe your cat is recommended. Owners must always be sure to wash their hands, even if they wore gloves, after bathing their cat.

Generalized Infection with Additional Factors

Many veterinarians will add oral anti-fungal medications for these more complicated cases. This is often the case if there was little to no success with localized, topical treatment, a large area is affected, multiple pets are involved, or if there are young or immunocompromised individuals in your home. Typically treatment with oral anti-fungal medications lasts for a minimum of 6 weeks. There are cases where a longer time period is necessary. It is generally standard for there to be two-in-a-row negative ringworm cultures before treatment is stopped.

Treatment will last anywhere from several weeks to months, depending on the severity of the infection and your cat’s response to treatment.


To help minimize spread, confine your cat, regardless of the severity of the infection, to a room that can easily be sanitized and is away from any other pets. Ideally, a room with a window so that the room can be aired out. If you do not have a room to isolate your cat into, an oversized crate will work as well. The whole idea is to keep fur and dandruff from spreading everywhere, so there's less to clean and disinfect, and it's easier to protect other pets and people in your home.

It is important to note that if treatment is stopped too early and proper environmental management is not done (see below), reinfection can occur. Re-infection can occur as well if your cat is a carrier. A carrier is a cat that transmits ringworm to the environment and/or animals and people while showing no signs of infection. It is estimated that about 20% of cats are carriers.

The fungal spore can live in the environment for up to 18 months, so continue environmental sanitization for a period of time even after other treatments have stopped.

Environmental Sanitation

It is also important to sanitize your home after each bath and wherever your cat has been before diagnosis, as well as where they are confined to during quarantine. Diligently clean up and carefully remove all fur from all floors and furniture. Daily sweeping and vacuuming is recommended during the whole treatment period. Then damp mop the areas with a solution of chlorine bleach and water. This solution will kill the fungus. To make a solution, dilute one pint of bleach in one gallon of water. In addition to damp mopping, wipe down all surfaces carefully. If possible, remove your cat from the room while it's airing out and the floor is drying.

Remember to wear gloves while sanitizing and wash your hands when done. Be sure to change your clothes and wash them as soon as you finish sanitizing or handling your cat.

How Do You Know Things Are Improving?

You will usually start to see improvement after about 2 to 3 weeks of treatment. The fur will begin to grow back and the lesions will lessen.

How Do You Know When Things Are Not Improving? What You Should Do.

If your cat continues to get more lesions and has continued hair loss beyond the first two weeks of treatment, contact your veterinarian. It may be necessary to add or change medications (topical and/or anti-fungal). Additionally, your cat’s veterinarian may need to perform more diagnostic tests to ensure that no other health issues are affecting your cat’s immune system.

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How to Prevent This from Happening in the Future

The best way to prevent ringworm from affecting your cat is to help support their immune system and to diligently decontaminate the environment. Some ways to do this are:

  • Keep your cat on a complete and well-balanced diet that provides them with the proper nutrients to help keep their immune system strong.
  • Provide pre- and probiotics because good gut health is essential to a good immune system.
  • If approved by your veterinarian, fish oils may benefit.
  • Place a dehumidifier in your cat’s main room. Ringworm, like other fungi, likes a moist environment.
  • Daily vacuum and dust up all pet hair and dandruff and mop or wipe down all surfaces (with diluted bleach* if possible) where cat hair and dandruff can be.
  • Daily disinfect crates or carriers.
  • Daily wash all toys, bowls, and brushes – using diluted bleach*.
  • Wash all bedding and blankets in hot water and bleach if possible.
  • Discard items that can't be fully sanitized.
  • Be aware of what other animals your cat comes into contact with.

*Diluted bleach: combine one pint of bleach with one gallon of water. Rinse anything you use this solution on thoroughly.

Cats that go outside or spend time with dogs that spend a lot of time outdoors can be bathed once or twice a week in an antifungal shampoo recommended by your veterinarian. This can also be done with your other pets that are outside a lot.

Any time after handling your pet or sanitizing, be sure to remove your clothes as soon as possible since they can spread the fungal spores if contaminated.

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