Ringworm in dogs and cats: symptoms, treatment and prevention

Summary

What is ringworm?

Ringworm, also called dermatophytosis, is caused by a fungus known as dermatophyte. These infect keratin-containing structures, including the outer skin layers, hair and claws.

Dermatophyte germination is much more common in warm, humid environments with high population density.

Several fungal species can cause infection. Microsporum canis is particularly important in cats and can also infect dogs and people.

Although ringworm is usually a superficial skin disease, it needs an appropriate management plan because of its ability to spread.

Expert advice from Dr Felicia:

In healthy adult animals ringworm can sometimes self resolve but this typically takes around 4 months, and is not recommended because of the infectious nature of disease.

How do dogs and cats get ringworm?

Pets can become infected through contact with an infected animal or contaminated material, such as shed hair, bedding, grooming equipment or surfaces. Some dermatophytes also occur in soil.

Exposure does not necessarily result in infection, as the skin has some defence mechanisms via the hair coat, grooming and the skin’s immune system. As such, skin microtrauma needs to occur for infection to occur. Young animals and pets in crowded environments may be more susceptible.

Infected hairs can carry fungal spores into the home. These spores can remain infectious for many months, which is why cleaning is part of treatment.

Expert advice from Dr Felicia:

Often kittens and puppies from shelters will have picked it up from the higher density, humid environment prior to coming home. Lesions tend to be evident after 1-3 weeks after infection.

Can a pet spread ringworm without visible symptoms?

Yes. Some pets have infection with few obvious signs. Others carry spores on their coat after contact with contaminated surroundings without having an active skin infection.

A positive coat test therefore needs to be interpreted alongside the examination and other findings. Ask your vet whether other household pets should be examined or tested.

What does ringworm look like?

Possible signs in dogs and cats include:

• Circular or irregular patches , non-symmetrical areas of hair loss
• Broken or stubbly hairs
• Scaly skin
• Itching, which may be absent, mild or more noticeable
• Occasionally, abnormal or brittle claws.

Expert advice from Dr Felicia:

There are many potential causes of these haircoat changes in dogs and cats, so it is important that the suspicion for ringworm is based on examination and that testing supports the diagnosis, especially since treatment involves oral medication, topical treatment and cleaning the environment.

Ringworm in dogs

Lesions may occur on the face, ears, feet, tail or elsewhere. Some dogs develop raised, inflamed nodules.

Bacterial skin infections and mites can look similar. A circular bald patch does not confirm ringworm.

Ringworm in cats

Hair loss and scaling commonly affect the face, ears and paws, although lesions can occur anywhere. Long coats can conceal affected areas, and some cats show only small patches or scattered crusts.

Appearance alone cannot reliably identify the cause.

When should I contact my vet?

Arrange an appointment if your pet develops unexplained bald patches, scaling or crusting, particularly after contact with an affected animal.

Tell the clinic you suspect ringworm before arriving so staff can advise on precautions. Seek more urgent advice if your pet is also unwell or has painful, extensive skin lesions.

Avoid applying creams or starting treatment before speaking with your vet, as this can affect assessment and testing.

How is ringworm diagnosed?

Diagnosis of ringworm is usually based on clinical suspicion and supportive test results because no gold standard diagnostic test exists. Your vet will examine your pet and may combine several tests, some of which are performed in house or may be sent away to a reference laboratory:

• Wood’s lamp examination: A special ultraviolet lamp helps identify certain infected hairs. Not all infections fluoresce, and some other materials can glow.
• Microscopy: Examination of hairs and skin material may reveal fungal structures.
• Fungal culture: Helps identify viable fungi and can assist with monitoring; takes up to two weeks.
• PCR testing: Detects fungal DNA and may provide faster results, however, it cannot differentiate between a carrier and a truly infected dog/cat.

No single test answers every diagnostic question, and results need to be interpreted in context.

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How is ringworm treated?

Treatment depends on the extent of infection, your pet’s health and the household situation. It often combines:

Oral antifungal medication

Prescription antifungals treat infection within the hair follicles. Your vet selects the medicine and schedule appropriate for your pet.

Treatment of the coat

Medicated shampoos, rinses or dips reduce infectious material on the coat. Whole-coat treatment may be recommended even when only a few patches are visible.

Cream applied to individual patches may be an additional treatment rather than a complete solution.

Expert advice from Dr Felicia:

Usually, topical shampoos need to be administered twice weekly over the treatment period.

Environmental cleaning

Removing contaminated hair and cleaning your pet’s surroundings helps reduce exposure and reinfection. Cleaning also helps to minimise carriage of dermatophytes on the fur which can interfere with assessing whether the infection has resolved.

Use only products recommended for your pet. Do not shave or clip affected areas yourself; clipping can damage the skin and spread contaminated hair.

How should I clean my home?

Focus on areas and items your pet uses:

1. Remove shed hair and debris by vacuuming or wiping.
2. Wash hard surfaces with detergent before disinfecting.
3. Use a suitable disinfectant recommended by your vet, following its dilution and contact-time instructions.
4. Launder bedding, towels and washable covers with detergent.
5. Clean grooming tools, carriers and other shared equipment.

Never apply household disinfectants to your pet or mix cleaning products. Keep pets away from treated surfaces until it is safe for them to return.

A comfortable area that is easy to clean can make management simpler. Follow your vet’s advice about separating pets while maintaining appropriate care and interaction.

Can people catch ringworm from pets?

Yes. Ringworm can pass between animals and people through direct contact or contaminated material. Bear in mind there has to be skin micro-trauma in order for infection to occur.

Wear gloves and long sleeves when providing treatment, wash your hands afterwards and avoid sharing beds or close skin contact while your pet is infectious. Children and people with weakened immune systems are at greater risk of becoming infected.

If someone develops an itchy, scaly rash or unexplained hair loss, contact a healthcare professional and mention the pet’s diagnosis.

Do not use a pet’s medication on a person. Steroid creams can worsen human ringworm and should not be used for a suspected infection without medical advice.

Expert advice from Dr Felicia:

Be aware that even while undergoing treatment your pet can still spread ringworm. Make sure to actively avoid your pet coming into contact with immunosuppressed people in the home and on walks.

How long does treatment take?

Treatment commonly takes several weeks and sometimes longer. Visible skin improvement does not necessarily mean the infection has cleared.

Continue medication and cleaning as directed. Your vet may use repeat examinations and fungal testing to decide when treatment and separation precautions can stop.

Most otherwise healthy pets recover well with an appropriate plan.

Managing ringworm successfully

Ringworm is usually manageable, but clearing it requires attention to both your pet and their surroundings. Follow the treatment plan, keep up with cleaning and attend follow-up checks before stopping precautions.

Sources:

“Dermatophytosis in Dogs and Cats”, Merck Veterinary Manual, updated February 2025. https://www.merckvetmanual.com/integumentary-system/dermatophytosis/dermatophytosis-in-dogs-and-cats. Accessed 22 October 2026.

“Ringworm (Dermatophytosis) in Dogs”, Merck Veterinary Manual, updated June 2026. https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/ringworm-dermatophytosis-in-dogs. Accessed 22 October 2026.

“GUIDELINE for Dermatophytosis, ringworm in cats”, European Advisory Board on Cat Diseases, updated March 2026. https://www.abcdcatsvets.org/guideline-for-dermatophytosis-ringworm-in-cats/. Accessed 22 October 2026.

“Diagnosis and treatment of dermatophytosis in dogs and cats. Clinical Consensus Guidelines of the World Association for Veterinary Dermatology”, Veterinary Dermatology, published May 2017. https://onlinelibrary.wiley.com/doi/10.1111/vde.12440. Accessed 22 October 2026.

“4.1 Dermatophytosis – Dogs and Cats”, University of Minnesota, Small and Large Animal Dermatology Handbook, Vol. 1. https://open.lib.umn.edu/animaldermatology/chapter/dermatophytosis-dogs-and-cats/. Accessed 22 October 2026.

“Ringworm: Keeping Your Pets & Family Safe”, Animal Management in Rural and Remote Indigenous Communities (AMRRIC). https://www.amrric.org/wp-content/uploads/2023/11/20231110-Dermatophytosis-Handout_D1.pdf. Accessed 22 October 2026.

“Treatment of Ringworm”, Centers for Disease Control and Prevention, updated February 2026. https://www.cdc.gov/ringworm/treatment/. Accessed 22 October 2026.