ringworm in dogs and cats: signs, spread, and treatment

Ringworm is not actually a worm at all, but a fungal skin infection, unrelated to intestinal parasites. In dogs and cats, it typically causes patches of hair loss, scaling, crusting, and redness. The classic image is a circular, ring-shaped patch, but the pattern doesn't always show up that way.

Ringworm spreads through contact with an infected animal or person and through contaminated objects such as bedding, brushes, carriers, and furniture. It can also spread from pets to people.

A veterinarian needs to test a suspicious skin lesion to confirm ringworm because allergies, mites, and bacterial skin infections can also look similar. Treatment typically combines antifungal medication with environmental cleaning to reduce the chances of reinfection.

If your dog or cat has a suspicious patch of hair loss or scaly skin, book an exam with a Banfield veterinarian. Be sure to mention any recent contact with other animals, shelters, boarding facilities, or pets with similar skin problems. Get your pet’s skin checked

Is ringworm actually a worm?

No. Ringworm is a fungal infection of the skin, hair, and sometimes claws. The medical term is dermatophytosis, and microsporum canis is one of the most common fungi responsible for ringworm in cats and dogs.

The name comes from the circular appearance ringworm can have on human skin, not from the presence of a worm. Because ringworm is caused by a fungus, deworming products do not treat it. Ringworm requires antifungal medication. For information about intestinal worms, read more about worms in dogs and cats

What does ringworm look like on a dog or cat?

Ringworm commonly causes circular or irregular areas of hair loss with scaling, flaking, crusting, or redness. Short, broken hairs around a lesion can give the coat a moth-eaten appearance. Common locations include the face, ears, paws, and tail, although ringworm can occur anywhere on the body.

Some pets have very little itching, while others scratch or groom affected areas frequently. Cats can also have infected claws or nail beds, which may become brittle or abnormal.

Longhaired cats can sometimes carry and spread ringworm with few obvious skin changes. This means you cannot confirm ringworm just by looking at a patch of skin. A veterinarian may need to test hair or skin samples to tell ringworm from other conditions that cause hair loss and scaling.

How do pets get ringworm?

Pets can get ringworm through direct contact with an infected animal or person or by contacting contaminated objects and surfaces. Bedding, brushes, grooming equipment, collars, carriers, furniture, and carpet can all carry fungal material shed by an infected pet.

The fungal spores can remain in the environment for an extended period. However, they do not multiply in the environment. Regular removal of hair and debris through vacuuming and cleaning helps reduce contamination.

Kittens and puppies as well as ill pets or those suffering from other physical stress are more susceptible. Crowded environments such as shelters and some boarding facilities can also increase exposure.

If your pet has another skin or coat problem and you are trying to understand the possibilities, see our pet parasite guide

How is ringworm diagnosed?

A fungal culture has long been the standard way to confirm ringworm, though it takes patience — typically about one to three weeks. PCR testing is a faster alternative, returning results in just a few days, and many veterinary teams use it alongside a culture rather than in place of one.

A Wood's lamp, the special light sometimes used to check for fungal infection, is a useful screening tool but not a diagnosis on its own. It helps your veterinarian spot suspect hairs worth sending off for microscopy or culture. Fluorescence under the lamp points toward ringworm, but it doesn't confirm it by itself, and plenty of true infections don't glow at all.

Part of the diagnostic process is ruling out other things. Your veterinarian will also consider allergies, mange, and bacterial skin infections, since these can look similar on the surface. No single test qualifies as a definitive gold standard, which is why your veterinary team may run more than one in combination rather than relying on just one result.

During a skin exam at Banfield, the veterinary team may ask when you first noticed the lesion, whether it is spreading, whether your pet is itchy, and whether other pets or people have developed skin problems. They may collect hairs, scales, or other samples from the affected area.

Treatment commonly takes several weeks or longer. Stopping treatment because the skin looks better can allow infection to persist or return. Follow the veterinary schedule and recommendations for follow-up testing. Other pets in the household may also need to be examined, even if they do not have obvious skin lesions.

Should you try to treat ringworm at home on your own?

It's worth holding off on any over-the-counter product before the exam. Treating the area yourself, even with something mild, can obscure what the veterinary team is trying to see and complicate an accurate diagnosis.

Because allergies, mites, and bacterial infections can look similar, avoid starting an over-the-counter treatment before the exam. Treating the wrong condition can make it harder to determine what is causing the skin problem.

How do I clean my home during treatment?

Environmental cleaning is part of ringworm management because infected hairs and spores can remain in the home and contribute to continued exposure. Your veterinary team can guide you on a cleaning plan.

The goal is to remove infected hair and other organic material from the environment, then disinfect surfaces. Thorough cleaning is an important part of reducing environmental contamination.

A practical routine includes:

• Vacuum frequently, including carpets, furniture, and other areas where your pet spends time.
• Dispose of vacuum debris outside when possible, or empty and clean the canister according to the manufacturer's instructions.
• Wash bedding, towels, and soft toys using the hottest setting the material safely allows.
• Remove loose hair and other debris from hard surfaces before disinfecting them.

Ask your veterinary team which disinfectant is appropriate for your home. Not every household cleaner works against fungal spores. When practical, keep your pet in areas that are easier to clean during treatment.

Can I catch ringworm from my pet?

Yes. Ringworm can spread from infected pets to people. In people, it commonly causes a red, scaly, sometimes itchy rash that may have a ring-shaped appearance. Children, older adults, and people with weakened immune systems may be more vulnerable to infection or complications.

Cats can carry ringworm without showing any visible signs. If you’re diagnosed with ringworm, your doctor may recommend having your cat examined and tested, even if their skin and coat look normal. Dogs with ringworm are more likely to have visible signs, such as patches of hair loss, scaling, or crusting, but an exam may still be needed to confirm the cause.

Ringworm FAQs

When to contact your veterinary team

Book an exam if your dog or cat develops:

• a circular or irregular patch of hair loss
• scaling, flaking, redness, or crusting
• a skin lesion that is spreading
• hair loss or scaly skin in a new kitten or puppy
• brittle or deformed claws
• similar skin lesions developing in another pet or person in the home

A suspicious patch does not necessarily mean ringworm. Allergies, mites, bacterial infections, and other skin conditions can cause similar signs, so testing is important before choosing treatment.

Contact your veterinary team before using a home remedy or over-the-counter product on a suspicious lesion. The wrong treatment may irritate the skin or make it harder to determine the cause.

If your pet is being treated for confirmed ringworm, follow-up testing may be needed to confirm the infection has cleared before you stop isolation or reduce environmental cleaning.

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Important Notice: The information provided on this page is for informational purposes only and is not a substitute for professional veterinary advice. Always consult a veterinarian with any questions regarding your pet's health or medical condition. Never disregard or delay seeking professional veterinary advice based on information from this page.