What is Ringworm in Cats and Dogs
Ringworm is a contagious fungal infection caused by a group of fungi known as dermatophytes, with Microsporum canis being the most common cause in cats and dogs. Despite its name, ringworm is not caused by a worm.
Ringworm fungi infect the hair shafts and outer layers of skin, often causing hair loss and red, crusty skin, sometimes in a circular pattern.
Ringworm is more common in kittens, puppies, older pets and animals with weakened immune systems. Long-haired cats, particularly breeds such as Persians, may be more prone to infection.
Some pets may have only mild signs, while others develop more obvious skin lesions. Ringworm can spread from animals to people and to other pets through direct contact. Fungal spores can also survive in the environment and spread on items such as bedding, towels and grooming equipment, which is why environmental cleaning is an important part of treatment.
The good news is that ringworm is treatable, although successful treatment often involves medication as well as environmental cleaning.
Written by Gillian Burkhill, Veterinary Surgeon, Animal Trust Vets CIC | Published May 2026 | Review date May 2029 | This advice is for UK pets only and is not a replacement for seeing a vet
Symptoms of Ringworm
Signs of ringworm can vary, but common symptoms include:
Circular patches of hair loss
Red, crusty or flaky skin
Broken hairs or poor coat quality
Itching (although some pets are not itchy)
Some cats, especially long-haired cats, may show only subtle signs such as dandruff or excessive grooming, and some pets may carry ringworm with few obvious symptoms.
Because these signs can resemble other skin conditions, veterinary assessment is important for an accurate diagnosis.
When to contact your vet
Contact your vet if your dog or cat develops areas of hair loss, scaly skin, broken hairs or other persistent skin changes, especially if the lesions are spreading.
You should also seek veterinary advice if:
Your pet is itchy or uncomfortable
Skin lesions are worsening or not improving
Other pets in the household have similar signs
Anyone in the household has developed suspicious skin lesions (they should contact their GP or healthcare provider for advice)
Because ringworm can look like many other skin conditions, a veterinary examination is important for accurate diagnosis and appropriate treatment.
Diagnosis
Ringworm can look similar to other skin conditions, so testing is often needed to confirm the diagnosis.
Your vet may diagnose ringworm based on your pet’s history, clinical signs and specific tests, which may include:
Examining hairs and skin under a microscope
Fungal culture to identify dermatophytes
Examining the skin and coat under an ultraviolet (Wood’s) lamp, as some strains of Microsporum canis may fluoresce
Because some pets can carry ringworm with few visible signs, testing may sometimes be recommended for in-contact animals as well.
Treatment of Ringworm
Ringworm is treatable, but treatment often takes several weeks and may involve both your pet and the home environment.
Treatment may include:
Antifungal medications prescribed by your vet
Topical antifungal treatment in some cases
Clipping of affected hair in some long-haired pets
Cleaning and disinfection of the home environment to reduce fungal spores
In households with multiple pets, other animals may also need to be checked or treated.
It is important to continue treatment as advised by your vet, even if the skin looks improved, as stopping too early can lead to recurrence.
Prevention of Ringworm
Reducing exposure to fungal spores can help lower the risk of ringworm.
Prevention measures include:
Isolating infected pets when advised by your vet
Cleaning bedding, grooming tools and the home environment regularly
Washing hands after handling infected animals
Avoiding contact with infected animals where possible
Having new pets checked if there is concern about infection
Prompt diagnosis and treatment can also help reduce spread to other pets and people.
Outlook
The outlook for pets with ringworm is generally very good, and most cases respond well to treatment.
Recovery can take several weeks, and in some cases longer, particularly in multi-pet households or where environmental contamination is significant. Following your vet’s treatment plan and cleaning recommendations is important for successful resolution.
Although recurrence can happen, most pets make a full recovery with appropriate treatment and management.