Ringworm in Cats and Dogs: Signs, Treatment and Hygiene

At a glance

What it is	A skin infection caused by fungi called dermatophytes, which live on hair and skin
Who's at risk	Kittens and puppies, longhaired cats, animals in shelters or multi-pet homes, and those with weakened immunity
Main signs	Patches of hair loss, often circular, with scaling or crusting; sometimes very few visible signs at all
Contagious?	Yes — to other animals and to people, by direct contact and through spores in the environment
Can it be prevented?	Not completely, but good hygiene and checking new pets early reduce the risk of spread

What it is

Despite the name, ringworm has nothing to do with worms. It is caused by a group of fungi that feed on keratin, the protein that makes up hair, the outer layer of skin and claws. The name comes from the ring-shaped rash it can cause in people.

Cats are the animal most commonly affected, and one particular fungus accounts for most cases in both cats and dogs. Some cats, especially longhaired ones, can carry the fungus in their coat without showing any signs, yet still spread it.

Infected animals shed tiny spores attached to broken hairs and skin flakes. These spores are tough. They can survive in the environment for many months — on bedding, carpets, furniture, grooming tools, carriers and in dust — and are a common reason infections keep coming back. Animals and people pick up the infection by touching an infected animal, or by contact with contaminated objects and surfaces. Broken or damp skin makes it easier for the infection to take hold.

In healthy adult animals, ringworm often clears by itself over a few months. However, treatment is still recommended because it speeds recovery, reduces the amount of spores shed and lowers the risk to people and other pets.

Signs to watch for

Ringworm can look very different from one animal to another, and it can mimic other skin problems.

• Round or irregular patches of hair loss, often on the face, ears, head and front legs
• Broken, stubbly hairs at the edge of patches
• Grey, scaly or dandruff-like skin
• Crusting, redness or small scabs
• Mild itching in some animals, though many aren't itchy at all
• Rough, brittle or misshapen claws
• In dogs, occasionally a raised, inflamed lump on the skin

Some cats, particularly longhaired breeds, show only subtle scaling or no signs at all. The symptom checker can help you think through skin changes, but a vet is needed to confirm ringworm.

Signs in people

In people, ringworm usually causes a red, itchy, scaly patch, often ring-shaped with a clearer centre, commonly on the arms, neck, face or scalp. Children, older people and those with weaker immune systems are more susceptible. If you or a family member develop a rash like this, see your doctor or pharmacist and mention that your pet has ringworm. People can treat their own infection without affecting their pet's treatment.

When to see a vet

Book an appointment if your pet has patches of hair loss, scaly skin or crusting, especially if they are young, newly adopted, or someone in the household has developed an itchy rash.

Ringworm itself is rarely an emergency. Contact your vet sooner if your pet:

• Has widespread skin lesions, broken skin or signs of a secondary infection such as pus or a bad smell
• Is very young, unwell, not eating or losing weight
• Has a known immune problem, such as FIV or FeLV in a cat

Ask your vet about precautions when you bring your pet in — they may suggest keeping them in a carrier and away from other animals.

How vets diagnose it

• Ultraviolet lamp examination. Under a special UV lamp, hairs infected with the most common fungus often glow apple-green. Not all types glow, so a negative result doesn't rule ringworm out.
• Microscopy. Plucked hairs can be examined under a microscope for fungal spores.
• Fungal culture. Hairs and scale collected by brushing the coat with a clean toothbrush are placed on a special growth medium. This can take up to a few weeks but identifies the fungus.
• Genetic tests (PCR) detect fungal DNA quickly, though they can't always tell live infection from dead spores.

Your vet may use these tests again during treatment to decide when your pet is clear.

Treatment and management

Successful treatment tackles the infection on the animal and the spores in the home at the same time.

• Medication by mouth. Antifungal medicine prescribed by your vet works from the inside to clear infection in hair follicles. It is usually given for several weeks.
• Topical treatment. Antifungal washes, rinses or dips applied to the whole coat kill spores on the surface and reduce spread. Treating isolated patches alone is not usually enough.
• Clipping, in some longhaired animals, to make topical treatment more effective — though this can spread spores, so your vet will advise.
• Treating in-contact animals. Other pets may need checking or treatment, even without signs.
• Follow-up tests to confirm the infection has cleared. Signs often improve before the infection is gone, so stopping too early risks a relapse.

Use only the treatments your vet recommends. Some antifungal products sold for people are not suitable for animals.

Cleaning your home

Environmental cleaning is just as important as treating the animal.

• Confine the infected pet to an easy-to-clean room, ideally without carpet, during treatment.
• Vacuum and remove hair and dust frequently, disposing of the contents carefully.
• Wash bedding, blankets and soft toys on a hot wash, repeated if possible; throw away items that can't be cleaned.
• Clean hard surfaces first to remove dust and hair, then use a disinfectant your vet confirms is effective against ringworm spores.
• Clean carriers, grooming tools, scratching posts and cat trees.
• Wash your hands after handling your pet and wear gloves when applying treatments.

Living with it

Treating ringworm can take weeks to months, and it requires patience. Keep a simple schedule of medication, baths and cleaning so nothing is missed. Allow a little extra time and cuddles away from soft furnishings while your pet is confined. Keep children from sleeping with the pet until your vet says the infection has cleared.

Prevention

• Check new kittens, puppies or rescue animals for skin problems and keep them separate from other pets until checked by a vet.
• Don't share grooming equipment between animals without cleaning it.
• Keep bedding clean, and groom longhaired cats regularly so you notice changes early. Our grooming guide has tips.
• If you are adopting a kitten, our guide to bringing a kitten home covers early health checks.

Breeds more at risk

Any cat or dog can get ringworm, but longhaired cats, particularly Persians, are well known to be more likely to carry and develop infection and can be harder to clear. In dogs, terriers and other dogs that dig or hunt may encounter soil-dwelling fungi more often.