Getting rid of ringworm on a dog typically requires a combination of oral antifungal medication and topical treatment, and the process takes several weeks to months. Ringworm isn’t actually a worm. It’s a fungal infection that burrows into the skin and hair follicles, producing the characteristic circular patches of hair loss. Because the fungus sheds microscopic spores into your home and can spread to other pets and humans, treatment has three fronts: medication for the dog, topical therapy to reduce shedding, and cleaning your environment.
Oral Antifungal Medication
Most dogs with ringworm need oral medication. Localized infections (a single small patch) can sometimes be treated with topical therapy alone, but if the infection has spread to multiple areas or is worsening, oral treatment is the standard approach.
The two primary medications used today are itraconazole and terbinafine. Both are effective against ringworm fungi, and both are available in relatively affordable generic forms. Itraconazole can be dosed in several patterns: daily, one week on and one week off, or two weeks on and two weeks off. Your vet will choose a schedule based on the severity of infection. Nausea is the most common side effect. Terbinafine works best when given with food and cannot be used in pregnant or nursing dogs.
An older drug called griseofulvin still works but has largely been replaced because the newer options have better safety profiles. Griseofulvin also needs to be given with a fatty meal to absorb properly, making it less convenient.
Topical Treatment to Reduce Spore Shedding
Oral medication kills the fungus from the inside, but your dog’s coat is still covered in spores that can reinfect them or spread to others. Topical treatment addresses this. The most commonly recommended option is a lime sulfur dip, applied every five to seven days. This is effective but comes with some practical challenges: it smells strongly of sulfur, can stain light-colored fur, will discolor jewelry, and may turn your dog’s coat slightly yellow.
When using a lime sulfur dip at home, dilute it according to the label, wear gloves and safety glasses, and work in a well-ventilated area. Do not rinse or blow-dry your dog afterward. Put a protective cone collar on until the coat dries to prevent your dog from licking the solution. Keep it away from eyes and mucous membranes.
Medicated shampoos containing miconazole combined with chlorhexidine may also help, though chlorhexidine alone is not effective against ringworm. Topical ointments, sprays, and mousse products do not reliably sterilize the coat or prevent further fungal growth, so they shouldn’t be your only form of topical therapy.
Clipping Your Dog’s Hair
Clipping the fur helps reduce the number of spores your dog sheds into your home. If only one or two small patches are affected, your vet may recommend shaving just those areas. For more widespread infections, clipping the entire coat is often advised. Always use clippers rather than scissors to avoid accidentally cutting irritated skin. Carefully bag and dispose of the clipped hair, since it’s loaded with fungal spores.
Cleaning Your Home
This is the step many people underestimate. Ringworm spores can survive on surfaces, furniture, bedding, and carpet for months. If you treat your dog but ignore the environment, reinfection is likely.
Vacuum frequently, especially areas where your dog spends the most time. Wash bedding, blankets, and any fabric your dog contacts in hot water. Hard surfaces can be cleaned with a diluted bleach solution. While concentrated bleach or a 1:10 dilution was once recommended, that concentration is unnecessarily harsh for routine use. A more moderate dilution is sufficient for regular cleaning, and your vet can advise on the right ratio for your situation. Dispose of vacuum bags or empty canisters outside the house after each use.
How Long Treatment Takes
Plan for a minimum of six weeks of treatment, though many cases take longer. The tricky part is that a dog can look completely healed, with fur growing back and skin looking normal, while still carrying live fungal spores. Stopping treatment based on appearance alone is one of the most common mistakes owners make.
The gold standard for confirming a cure is a fungal culture, where your vet collects hair and skin samples and watches for fungal growth in a lab over one to three weeks. Most vets require at least one or two negative cultures before discontinuing treatment. This testing adds time, but it’s the only reliable way to know the infection is truly gone.
Protecting Yourself and Other Pets
Ringworm is zoonotic, meaning it spreads from animals to people. The circular, red, itchy patches it causes on human skin are the same fungus your dog is carrying. The CDC recommends several precautions while your dog is being treated:
- Wear gloves and long sleeves when handling your dog, applying dips, or cleaning contaminated areas.
- Wash your hands with soap and running water after every contact with your dog.
- Bring other pets in for evaluation. Even animals without visible lesions can carry spores. Cats are especially susceptible to the same species of ringworm that infects dogs.
- Limit your dog’s access to shared furniture and carpeted rooms when possible to reduce the areas you need to decontaminate.
Getting the Diagnosis Right
Before starting treatment, it’s worth confirming the diagnosis. Not every bald patch on a dog is ringworm. Bacterial skin infections, mites, and allergic reactions can look similar. A Wood’s lamp (a type of ultraviolet light) can sometimes make infected hairs glow, but this test misses many cases and works more reliably in cats than dogs. Fungal culture remains the most definitive diagnostic tool. A positive culture confirms fungal spores are present, and counting the number of colonies that grow helps distinguish a true infection from a dog that simply picked up spores on its coat without being infected.
If your dog has been diagnosed and you’re following through on oral medication, topical dips, hair clipping, and environmental cleaning, you’re covering all the bases. The process is slow and requires patience, but ringworm is curable, and most dogs recover fully without lasting effects.