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A dog with a stethoscope around its neck lying on the floor, holding a stethoscope in its mouth.
Pet Blog

Understanding Ringworm Infections and How to Help Your Pet

Does your pet have red, balding patches on their skin? It could be ringworm. Learn more about symptoms, treatment, and how to keep ringworm infections at bay.

What is Ringworm?

Ringworm might sound scary, but it’s a very common and typically non-threatening infection that affects the skin and hair of both animals and people. Good news for people who don’t like creepy crawlies—ringworm isn’t a worm at all! It’s actually the colloquial name for a fungal infection.

Ringworm (scientifically known as tinea corporis) is caused by a collection of disease-causing bacteria known as dermatophytes. Almost all ringworm infections are caused by three types of fungus:

  • Microsporum canis, responsible for about 70% of infections
  • Microsporum gypseum, responsible for about 20% of infections
  • Trichophyton mentagrophytes, responsible for about 10% of infections

These fungi are found in nature and will hitch a ride home on your pet’s fur, where they can be spread to other animals and humans. The fungus takes up residence on the skin’s surface, in hair follicles, and occasionally in the nails, causing skin irritation and weak hair and nails.

Almost all pets will be exposed to these fungal dermatophytes throughout their lifetime, but many pets have a strong enough immune system to keep infection at bay. Dogs and cats who are very young, old, or immunocompromised are more likely to develop symptoms and may experience more severe infections than healthy adult pets.

Ringworm is actually a common infection in humans too, but we know it by several different names depending on where the infection is located. Red, ring-shaped patches of irritated skin are referred to as ringworm when found on the scalp and much of the body, but the same fungi affecting the feet are called athlete’s foot!

Symptoms & Diagnosis

Cases of ringworm can present in a range of ways, but you should watch out for any of these common symptoms of ringworm in dogs and cats:

  • Circular patches of hair loss
  • Red, irritated skin or skin lesions
  • Scaly or flaky skin
  • Dry, brittle hair that may break easily
  • Peeling or cracking nails
  • Small, sesame seed-sized scabs called miliary dermatitis (more common in cats)

If you notice any of the above signs or see that your pet seems to be itchy or in pain, you should head to your vet for a diagnosis. They’ll examine your pet’s skin and fur and will most likely use these common methods to confirm that the infection is ringworm:

  • Wood’s lamp: This ultraviolet lamp makes the excretions of the infectious fungi glow bright yellowy-green under the light. It doesn’t detect all cases so further testing is typically done, but is a good non-invasive preliminary test to identify ringworm.
  • Microscopic examination: Your vet may take a hair sample from the affected area and examine it under the microscope to visually identify fungal spores on the hair.
  • Fungal culture: If they still need to confirm the diagnosis, your vet will send a hair sample into a laboratory to test and identify the fungus. This test may take up to a month for a conclusive diagnosis, so it typically isn’t the first test vets reach for, but it is the most accurate.

If your vet believes your pet is experiencing a severe ringworm infection, they may recommend further lab tests to assess your pets’ general immune health. Most adult animals are healthy enough to fight off ringworm infections, and a major systemic infection may be a sign of an undiagnosed medical issue that’s compromising their immune response.


If your pet gets an official diagnosis of ringworm, your vet will help you develop a treatment plan for your pet. There are three common things your vet will prescribe to treat ringworm:

  • Topical creams or ointments: These treatments are applied directly to the skin in affected areas and work best for localized infections. Your vet may recommend shaving these areas on longhaired pets to make application easier. In addition to fighting the fungus and soothing your pet’s skin, these treatments also help to trap spores and prevent them from spreading.
  • Medicated shampoo: If your pet has a widespread infection across large areas of their body, a full body shampoo may be the easiest way to tackle it. Vet-prescribed medicated shampoos use similar ingredients to antifungal creams, but are formulated to be effective even after being rinsed off.
  • Oral medications: Vets will often prescribe a systemic oral medication to use along with topical treatment to attack the infection from the inside out. There are several different medications available, typically given as a pill given with their meals. Your vet may require periodic blood tests to check for side effects while your pet is on the medication, as some popular medications can suppress the function of bone marrow, reducing your pet’s red and white blood cell counts. With proper vet supervision, these treatments can be safe and effective!

No matter which medications your vet prescribes, they will need to take them for a minimum of six weeks to complete the course of treatment and may need to take them for several months for the infection to clear completely. Your vet will also likely recommend that other pets in the household and humans who have had close contact with the infected animal should be tested for ringworm. Catching infections early can help to make the treatment process easier!

Another key element of battling ringworm is upping your cleaning routine as soon as your pet is diagnosed with ringworm and continuing to keep things as sanitary as possible while your pet is recovering. Fungal spores can easily spread to your hands when you give your pet belly rubs or transfer to your couch cushions when your pet takes a nap, ready and waiting to hitch a ride on whoever sits down next.

To combat the spread of ringworm, you should:

  • Thoroughly vacuum rugs, furniture, and other soft surfaces your dog has contact with daily.
  • Regularly wash pet beds, blankets, soft toys, and furniture slipcovers.
  • Disinfect any hard surfaces your pet frequents daily.
  • Immediately contain and dispose of shed hair from brushing your pet.
  • Temporarily swap out soft toys and snuffle mats full of nooks and crannies with easy-to-clean toys that can be scrubbed clean or machine washed.
  • Minimize physical contact with your pet as much as possible while they’re completing treatment and consider isolating them from other pets and young children who can’t resist the appeal of a pet begging for attention.
  • Wash your hands thoroughly after any contact with your pet.
  • Keep any infected pets away from any people with weakened immune systems who are more vulnerable to a ringworm infection.

Containing the spread can be emotionally challenging, especially for snugglebug pets who don’t understand why you can’t have your daily cuddle session. Just know you’re doing the best thing possible to protect your pet’s health and your own—and there are lots of bellyrubs waiting for you both when they get a clean bill of health!


While we all want to keep our pets safe from anything that could harm them, the unfortunate truth is that there’s no way to entirely eliminate the chance of your pet coming into contact with the fungi that cause ringworm. However, there are still things you can do to reduce the chances of that contact turning into an infection! Your best lines of defense are consistent cleaning and supporting your pet’s immune health.

While it may not be realistic to vacuum every surface in your house daily all the time, regularly cleaning the high-traffic items and locations your pet loves can help to keep the amount of pesky fungal spores in your house down and lower everyone’s chance of infection. Keeping a checklist of things to clean weekly and monthly will help to keep you on track and support a healthy environment for everyone in your home.

A strong and healthy immune system can be the key to stopping an infection in its tracks! There are many natural ways to support your pet’s immune health, like making sure they’re physically active, getting them out into nature, and feeding a diet that nourishes them and actually improves body function. Adding an immune support topper to your dog or cat’s dinner or letting your cat snack on immunity-boosting treats is an easy way to ensure they’re getting vital nutrition without them even knowing they basically just took their vitamins!

The good news is that ringworm is a manageable problem and knowing the basics will help you take even better care of your best friend. Whether you’re diagnosing their pesky skin infection or taking preventative measures to keep them healthy, your pet will know they’re in good hands—as always.