Ringworm in Dogs: Causes, Stages, and Treatments

Ringworm is a common fungal skin infection in dogs that is highly contagious and has zoonotic potential. Ringworm is caused by Microsporum and Trichophyton species through direct or indirect contact. 

Young puppies, seniors, and immune-compromised dogs are at an increased risk of infection. Other risk factors include breed, poor hygiene, overcrowded places, stress, and chronic skin conditions. 

Circular skin lesions with ring-like edges and elevated, hairless surfaces are the telltale signs of ringworm in dogs. The hair around the lesions is covered with dandruff and brittle, and the skin darkens. 

Ringworm on dogs is diagnosed by examination using Wood’s lamp, fungal cultures, and PCR testing. The ringworm treatment for dogs is isolation, lime sulfur dips, and antifungals. CBD oil is a useful natural treatment addition. 

What is Ringworm in Dogs?

Ringworm in dogs is a contagious, zoonotic, and fungal skin infection. Ringworm has nothing to do with worms, despite its namesake. 

The medical term for ringworm is dermatophytosis, derived from the specific ring-like lesions caused by the fungus. 

Ringworm in dogs is caused by two fungal species, Mycrosporum and Trichophyton. The fungi live on the surface of the skin, hair, and nails, feeding on dead skin or hair cells. 

Dog skin allergies and other itchy chronic skin conditions increase the risk of infection because the fungus enters through damaged skin. 

Dogs periodically transmit the fungus without signs of infection. Ringworm is common in dogs but manageable and rarely associated with severe consequences. 

What Causes Ringworm in Dogs?

The causes of ringworm in dogs are listed below. 

• Microsporum canis: M. canis is the number one cause of ringworm in pets and is responsible for 70% of dog infections. The fungus affects the dead upper layers of the skin and is distributed worldwide. 
• Microsporum gypseum: M. gypseum is a highly contagious fungus in soil that causes dermatophytosis in pets and humans. The species causes 20% of ringworm cases in dogs. 
• Trichophyton mentagrophytes: T. mentagrophytes is the rarest cause of ringworm in dogs, responsible for 10% of the cases. The fungus is zoonotic, highly contagious, and present worldwide. 

What is Early Stage Ringworm in Dogs?

The early stage of ringworm in dogs is incubation. Incubation is the timeframe between initial contact with the infection source and the emergence of symptoms. Stage one, or incubation for ringworm, lasts one to three weeks. 

The other three stages of ringworm in dogs are marked by specific symptoms. Small and raised skin bumps emerge in stage 2. The lesions enlarge and merge in stage 3. The skin infection generalizes in stage 4. 

How do Dogs Get Ringworm?

Dogs get ringworm through direct or indirect contact with infected animals or soil. The most common source of infections is direct contact with a ringworm-carrying animal. 

Indirect contact occurs when a dog uses bowls, toys, or bedding from an infected dog. Certain ringworm-causing fungi live in the soil and, when discovered, infect dogs. 

Atopic dermatitis, a type of dog allergy, damages the skin barrier and increases the risk of getting ringworm. Food and environmental allergies contribute to the infection risk. 

What Are the Symptoms of Ringworm in Dogs?

The symptoms of ringworm in dogs are listed below. 

• Skin Lesions: Ringworm causes raised, red, and well-defined circular skin lesions with ring-like edges. The area over the lesions loses hair, and the skin becomes dry and scaly.
• Dandruff: Excessive dandruff production, especially in the hairless lesions, is a sign of ringworm infection in dogs. 
• Dark Skin Patches: The skin becomes temporarily darkened in the advanced stages, a sign of prolonged skin irritation and damage. 
• Scratching: Ringworm is itchy in some dogs and not itchy in others. Itchy dogs scratch or rub themselves against surfaces. 
• Broken Hair: The dog’s coat is unkempt, with brittle hairs that fall off easily. 
• Nail Changes: Dry, dark, brittle, and misshapen nails with inflamed nail beds are visible in dogs with ringworm infections. 

How is Ringworm Diagnosed in Dogs?

Ringworm in dogs is diagnosed by physical examination, Wood’s lamp, fungal cultures, and polymerase chain reaction (PCR) testing. 

The physical exam assesses the dog’s overall state and identifies the characteristic-appearing ringworm skin lesions. 

The Wood’s lamp is a source of long-wave, black UV light. Shined with a Wood lamp, ringworm glows because the fungus causes a chemical reaction once attached to follicles. Asymptomatic dogs carrying the fungus do not glow under Wood’s lamp. 

Fungal culture (known as dermatophyte test medium or DTM) is performed when the veterinarian collects several hairs or scabs, places them on a culture medium, and examines them under a microscope.

The test's advantage is that it does not require active lesions and is accurate with any hair sample. The drawback is that the final result takes ten days to three weeks to arrive. 

PCR testing is a novel technique that detects fungal DNA on a hair sample. The test provides accurate and fast results that are ready within three to five days. 

How Contagious is Ringworm in Dogs?

Ringworm in dogs is highly contagious. The fungus is transmitted via direct or indirect contact. Direct is by touching an infected animal. Indirect is by handling or using objects of infected pets. 

Ringworm enters the body and causes infection through broken skin, such as cuts, scrapes, or wounds. Skin conditions like eczema serve as entry points for the fungus.  

A properly treated dog with ringworm remains contagious for around 21 days. Longer infectious periods are possible in immune-compromised dogs or if the treatment is not aggressive enough. 

Can Ringworm in Dogs Affect Humans?

Yes, ringworm in dogs can affect humans. Ringworm is a zoonosis and spreads from pets to humans and vice versa. 

People get ringworms through close contact with infected dogs and cats. Puppies and kittens are more likely to spread the fungus. 

Immune-compromised people, young children, and seniors are at a high risk of developing an infection after contact with ringworm dogs. 

What are the Treatment Options for Ringworm in Dogs?

The treatment options for ringworm in dogs are listed below. 

• Isolation: Dogs with ringworm infections must be quarantined. Direct contact with other household pets and people increases the risk of spreading the disease. 
• Bathing: Bathing is important for removing fungal spores attached to the dog. The two bathing options are lime sulfur dips and antifungal shampoos. Lime sulfur dips are more effective. 
• Topicals: Antifungal creams and ointments are used directly on the skin to treat ringworm lesions. Topicals are ineffective if used alone. 
• Oral Antifungals: Oral antifungals are essential and include various options such as griseofulvin, itraconazole, ketoconazole, fluconazole, terbinafine, and amphotericine B.  
• Hair Clipping: Hair clipping allows topical creams or shampoos to penetrate better but causes tiny injuries (microtrauma), which help the fungus spread. Consult the veterinarian to determine whether the benefits of hair clipping outweigh the risks. 

How Long Does it Take for Ringworm to Heal in Dogs?

It takes four to eight weeks for ringworm to heal in dogs. Some dogs respond quickly and show improvement within two weeks. Completing the treatment is critical for preventing recurring infections. 

The veterinarian uses a Wood's lamp to monitor the dog’s healing through fungal cultures and skin examinations. Most dogs recover completely and do not experience long-term effects. 

What are Home Remedies for Ringworm in Dogs?

Home remedies for ringworm in dogs include over-the-counter antifungal shampoos and natural treatments. OTC shampoos and natural treatments must not be used as a sole approach. Talk to a veterinarian to discuss a multimodal treatment plan. 

Popular natural treatments for ringworm include oregano oil, apple cider vinegar, and lemongrass essential oil. Natural remedies are less effective than mainstream treatments. 

How Can I Prevent Ringworm in My Dog?

The ways you can prevent ringworm in your dog are given below. 

• Maintain excellent hygiene in the house by vacuuming, steam cleaning, and dusting to eliminate potential spores. 
• Clean the dog’s bedding, bowls, and items regularly. Dispose of hair attached to brushes and other grooming tools. 
• Avoid overcrowded spaces at high risk for harboring ringworm fungi and other infectious diseases. 
• Support the dog’s immunity by providing quality food and practicing daily exercise. Give the dog immune boosters if necessary. 
• Create a comfortable and stress-free environment for the dog. Stress is a significant risk factor for ringworm infection. 

What Should I Do If My Dog Has Ringworm?

The things you should do if your dog has ringworm are given below. 

• Visit the veterinarian. Schedule an appointment with the veterinarian if suspecting ringworm. The vet examines the dog and gives treatment instructions. 
• Administer the prescribed treatment. Use the prescribed or recommended treatments as directed by the vet. Avoid discontinuing the treatment prematurely, even if the dog appears healed.  
• Avoid contact between the dog and other pets. Prevent the dog from making contact with other pets in the household and family members from risky categories, such as kids and seniors. 
• Stay mindful of hygiene. Wash hands thoroughly after interacting with the dog to reduce the risk of infection. Clean the environment and the dog’s belongings daily. 
• See the vet for a checkup. Follow-up with the veterinarian once treatment is complete. The vet evaluates if the dog is cured or needs further medication based on the findings.  

What are the Risk Factors for Ringworm in Dogs?

The risk factors for ringworm in dogs are listed below. 

• Breed: “Boston Terriers, Yorkshire Terriers, and Russell Terriers are genetically more prone to ringworm infections than other breeds,” explains an article “Ringworm in Dogs” published by PetMD in 2022. 
• Stress: Stress supports cortisol production, harming the strength of the dog’s immune response and increasing the risk of ringworm infections. Dogs infected with ringworm have longer recovery times if subdued to stress or anxiety. 
• Immunity Issues: Dogs with compromised or underdeveloped immune systems are at a higher risk of getting infected. Ringworm dog skin infections are widespread in puppies and seniors. 
• Skin Conditions: A dog skin infection that disrupts the protective barrier is an established risk factor for ringworm. Examples are chronic skin issues, open wounds, fresh scrapes or cuts, and flea infestations. 
• Poor Hygiene: Subpar hygiene in the dog’s environment and overcrowded living conditions are risk factors for ringworm infections. 

How Can I Clean My Home to Prevent the Spread of Ringworm?

The ways you can clean your home to prevent the spread of ringworm are given below. 

• Keep the dog confined to a single room or specific area of the house to limit the spread of the disease and make cleaning efforts more efficient. 
• Vacuum all soft furnishings and soft carpets thoroughly to remove spores. Steam cleaning is an excellent alternative to regular vacuuming. 
• Ensure the vacuum bag's contents are safely disposed of after cleaning. Burning is the safest option for objects that are unfit for cleaning. 
• Disinfect the dog’s items, such as toys, bowls, and grooming tools. Consult the vet and ask for help in choosing a disinfectant. A diluted bleach solution (10 parts water to 1 part bleach) is a good option. 

Can Ringworm Recur in Dogs?

Yes, ringworm can recur in dogs. Ringworm dog skin infections recur if the treatment is mild or prematurely discontinued. 

Mild treatment uses only topical antifungal instead of a combination of topical and oral meds. Premature medication discontinuation is when the owner stops treatment because the dog’s lesions appear better. 

A compromised immune system is another situation that increases the risk of ringworm recurrence. Puppies, seniors, and dogs with weak immunities are prone to infection recurrence. 

What Types of Medications are Used to Treat Ringworm in Dogs?

The types of medications used to treat ringworm in dogs are listed below. 

• Shampoos: Dog shampoos soothe the skin and provide itch relief. Certain shampoo formulations are medicated, meaning they contain an antifungal as an active ingredient. 
• Creams and Ointments: Creams and ointments are applied topically to skin lesions. Topical antifungals are combined with other treatments, such as shampoos and oral medications. 
• Oral Antifungals: Oral antifungals are the cornerstone of treating ringworm in dogs. The medications are used alone or combined with topicals. 

How Do I Know if My Dog’s Ringworm Treatment is Working?

You know if your dog’s ringworm treatment is working if there are signs of improvement. The hairless skin patches become larger at first, which is normal. 

Signs of improvement are visible around two weeks after the treatment is initiated. The lesions get less red and scaly. Hair slowly starts growing at the edges and fills the rounded lesions. 

See the vet if the dog is not showing signs of improvement within two weeks. The vet explains how to treat ringworm in dogs more successfully and based on the specific situation. 

Are There Any Side Effects of Ringworm Treatments in Dogs?

Yes, there are side effects of ringworm treatments in dogs. The golden standard for managing ringworm was griseofulvin. 

Common side effects of griseofulvin include stomach upset, sunlight sensitivity, and increased itchiness. Serious side effects are weakness, pale gums, abnormal bleeding, and fever.

Newer antifungals like itraconazole and terbinafine are now replacing Griseofulvin to minimize side effects. 

Modern antifungals trigger less severe adverse events such as stomach distress, abdominal pain, and skin reactions.  

Is Ringworm in Dogs Itchy?

Yes, ringworm in dogs is itchy. The exact level of itchiness, however, varies. Dogs constantly scratch ring-like skin lesions, while others do not show signs of discomfort. 

Itchy dogs are more likely to spread the fungus in the environment. Itchy dog skin is a red flag that warrants immediate veterinary attention. 

How Often Should I Bathe My Dog with Ringworm?

You should bathe your dog with ringworm shampoo twice a week. Different antifungal and ringworm shampoos have unique instructions, but two baths per week are the guideline. 

The vet recommends a shampoo product and explains the bathing frequency. The shampoo must be thoroughly applied for optimal efficacy and then rinsed well to avoid irritation. 

Can CBD Oil Relieve Ringworm in Dogs?

Yes, CBD oil can relieve ringworm in dogs. CBD has natural anti-inflammatory properties and soothes irritated skin. The antipruritic effect reduces itchiness and makes the dog comfortable. 

Dog CBD oil for ringworm support is part of a multimodal treatment. The oil is administered by mouth (orally) or applied directly on the irritated skin (topically).