Introduction
Ringworm is a highly contagious fungal infection of the skin that gets its name from its characteristic ring-like lesions. It is caused by several species of fungi in the genus Trichophyton or Microsporum. In dogs, ringworm often presents as round, bald patches with scaly skin. The edges of the lesions may appear red and inflamed. Ringworm can spread rapidly between dogs and to humans through direct contact or contact with contaminated objects.
Ringworm is concerning in dogs because it is zoonotic, meaning it can be transmitted to humans. It can also spread quickly in multi-dog households or environments like kennels and veterinary clinics if not treated properly. Some dogs may experience hair loss and secondary skin infections associated with ringworm. For these reasons, it is important for dog owners to recognize ringworm and seek veterinary treatment for affected pets.
Common Ringworm Lookalikes
There are several skin conditions that can be mistaken for ringworm in dogs. Some of the most common ringworm lookalikes include:
Allergies
Dogs can develop allergic reactions to things like food, flea bites, pollen, or chemicals. These allergies cause intense itching, redness, and sometimes hair loss which may resemble ringworm. Allergic dermatitis often affects the face, feet, belly, folds of the skin, and ears [1].
Bacterial Infections
Bacterial skin infections like folliculitis, impetigo, and pyoderma can cause itchy patches, pustules, crusty sores, and hair loss similar to ringworm lesions. Folliculitis often occurs in hairy areas like the legs and belly. Impetigo causes honey-colored crusts on the skin. Pyoderma leads to pus-filled bumps that can spread [2].
Yeast Infections
An overgrowth of yeast on the skin, known as Malassezia dermatitis, results in greasy red patches, scaling, hair loss, and a characteristic yeasty odor. It typically affects the paws, ears, elbows, and other moist folded skin. The affected areas are often itchy and irritated [3].
Allergies
Allergies are a common cause of skin irritation in dogs that can sometimes look similar to ringworm. Allergic reactions happen when a dog’s immune system overreacts to something in the environment that is normally harmless, like pollen or dust mites. This causes inflammation, redness, and itching of the skin.
With allergies, the rash and skin irritation is often symmetrical on both sides of the body and tends to be focused in areas like the face, feet, armpits, and groin. The skin may appear red and inflamed with bumps or pustules from scratching. There may be hair loss and scaly patches.[1]
Unlike ringworm which is caused by a fungal infection, allergies are not contagious. The rash from allergies also lacks the distinctive ring-shaped lesions caused by ringworm fungus. Allergy symptoms tend to fluctuate seasonally when the allergen is present. Ringworm lesions persist until treated.
To differentiate allergies from ringworm, a vet can perform tests like skin scrapings or fungal cultures. Treating the underlying allergy is key, through medications, immunotherapy, or avoiding the allergen source if identified.
Bacterial Infections
The most common bacterial skin infection in dogs is caused by the bacterium Staphylococcus sp. This infection, known as pyoderma or impetigo, leads to pus-filled pustules on the skin that cause hair loss, redness, papules, and crusty sores. Pyoderma is highly contagious between dogs and can spread quickly in multi-dog households.
According to Today’s Veterinary Practice, pyoderma often develops when there is an underlying condition that compromises the skin barrier, such as allergies or endocrine disorders. The bacterial infection then takes advantage of the weakened skin. Treatment focuses on addressing both the bacterial infection and underlying condition. Antibiotics such as cephalexporins are commonly prescribed (https://www.guilfordjamestownvet.com/site/blog-greensboro-vet/2020/11/30/bacterial-fungal-skin-infections-dogs).
Other bacterial skin infections include deep pyoderma, juvenile pyoderma, and opportunistic infections. These may lead to nodules, fistulas, and abscesses under the skin. Identifying bacterial infections requires veterinary cytology, cultures, or biopsy. At home, look for crusty, oozing lesions with hair loss, redness, and pustules. Seek prompt veterinary care, as delays can allow the infection to spread. Bacterial infections in dogs are contagious and require antibiotic treatment (https://www.fallsroad.com/site/tips-resources-blog-baltimore-vet/2020/12/11/bacterial-fungal-skin-infections-dogs).
Yeast Infections
Yeast infections, also known as yeast dermatitis or Malassezia dermatitis, are a common skin condition in dogs caused by the fungus Malassezia pachydermatis. Symptoms of a yeast infection include red, irritated skin; itching and scratching; flaky or scaly skin; greasy skin; and dark pigmented areas on the skin. The ears, muzzle, armpits, groin, and paws are common locations for yeast infections in dogs.
Yeast thrives in warm, moist environments. Things that can increase a dog’s risk of developing a yeast overgrowth include allergies, endocrine diseases, immunosuppression, antibiotic therapy, diabetes, and obesity. The itching and inflammation of a yeast infection are caused by an immune response to the yeast overgrowth on the skin.
To diagnose a yeast infection, a veterinarian will take a skin scraping and examine it under a microscope to look for an abundance of yeast organisms. They may also culture a skin sample to identify the specific type of yeast. Blood tests can help identify any underlying problems, such as diabetes or hypothyroidism, that may be contributing to the yeast overgrowth.
Treatment for yeast dermatitis includes antifungal medications, such as special shampoos, dips, and oral medications. Improving skin barrier function and reducing skin moisture can also help clear the infection. The vinegar rinse is a home remedy that may help change the pH of the skin to inhibit yeast overgrowth. However, other home remedies do not have scientific evidence of effectiveness [1]. Addressing any underlying health issues is also important for preventing recurring infections.
Mange
Mange is a skin disease caused by microscopic mites that burrow into the skin and cause irritation. There are two main types of mange in dogs:
- Sarcoptic mange – caused by the Sarcoptes scabiei mite. This is highly contagious and can spread between dogs or to people.
- Demodectic mange – caused by the Demodex canis mite. This mite is normally present in small numbers on all dogs. In dogs with suppressed immune systems or other issues, the mites can multiply rapidly causing mange. Demodectic mange is not contagious to other dogs or people.
Both types of mange cause intense itchiness, redness, and hair loss. Sarcoptic mange tends to cause patchy hair loss and thick crusty scabs. Demodectic mange often starts localized in small patches, especially on the face and legs. Without treatment, it can spread across the entire body causing widespread hair loss, leathery skin, and skin infections (AKC).
Mange differs from ringworm in that it is caused by mites rather than a fungal infection. The hair loss and skin irritation can look similar visually, but mange leads to thick crusty scabs whereas ringworm causes circular patches with lighter colored rings along the edges. Mange is highly contagious between dogs while ringworm transmission requires direct contact and is less contagious. Only sarcoptic mange is transmissible to people, not ringworm or demodectic mange.
Autoimmune Diseases
Autoimmune skin diseases are less common causes of skin problems that mimic ringworm in dogs. With autoimmune diseases, the immune system mistakenly attacks the body’s own healthy cells and tissues. This leads to inflammation, sores, and skin damage. Some examples of autoimmune skin diseases in dogs include:
- Pemphigus – Causes painful blisters and pustules on the skin and mucous membranes. The two main types are pemphigus foliaceus and pemphigus vulgaris.
- Discoid lupus erythematosus – Leads to loss of pigment and scaly, crusty sores often on the nose and face.
- Bullous pemphigoid – Causes large fluid-filled blisters on the skin.
- Panniculitis – Inflammation of the fatty tissues under the skin resulting in nodular lesions.
- Vasculitis – Inflammation of blood vessels leading to ulcers on the skin.
Diagnosing autoimmune skin diseases can be challenging and typically involves skin biopsies, blood tests, and ruling out other conditions. Treatment focuses on suppressing the overactive immune system with medications like corticosteroids, immunomodulatory drugs, and immunosuppressants.
While not as common as allergies or infections, autoimmune diseases are an important differential diagnosis for skin issues that initially resemble ringworm in dogs.
Diagnosis
Diagnosing ringworm lookalikes and distinguishing them from actual ringworm infections requires a veterinarian’s expertise. The vet will begin with a thorough physical exam, checking the dog’s skin and coat for any lesions, inflammation, hair loss, or other abnormalities. They will note the location, appearance, and distribution of any skin changes.
To aid in diagnosis, the vet may perform additional tests:
- Skin scrapings – Using a scalpel blade, the vet takes a superficial scraping of skin and examines it under the microscope for parasites like mites.
- Fungal culture – The vet collects a hair and skin sample to grow in a lab culture medium. This can identify the specific fungus present.
- Wood’s lamp exam – Ringworm fungus glows a certain color under ultraviolet light. This can help diagnose ringworm.
- Cytology – Microscopic examination of skin cells collected via swab or tape strips. This can identify yeast and bacteria.
- Biopsy – Removing a small skin sample for microscopic analysis. This provides definitive diagnosis.
Through these diagnostic tests, the vet can determine if the skin condition is truly ringworm or a lookalike disorder. Accurate diagnosis guides proper treatment.
Sources:
https://www.merckvetmanual.com/dog-owners/skin-disorders-of-dogs/diagnosis-of-skin-disorders-in-dogs
Diagnosing Common Skin Conditions of Dogs and Cats in Community Medicine Practice
Treatment
Treatment for skin conditions that mimic ringworm depends on the underlying cause. Bacterial infections are often treated with oral antibiotics like cephalexin or topical antibiotic creams prescribed by a veterinarian (Merck Veterinary Manual). Antifungal medications like ketoconazole may be used for yeast infections. For allergies, antihistamines, omega-3 fatty acids, and immunotherapy shots can provide relief. Medicated shampoos containing chlorhexidine, miconazole, or ketoconazole can also help treat and prevent recurrent infections. For autoimmune diseases, immunomodulating medications like cyclosporine may be prescribed. Mange mites are treated with topical parasiticides like selamectin. While treatment plans vary, most skin conditions are very manageable with veterinary care and diligence on the owner’s part. Consult a veterinarian to accurately diagnose the cause and determine an appropriate treatment plan.
Prevention
To help prevent ringworm lookalikes in dogs, keep their skin and coat healthy by feeding them a nutritious diet rich in Omega-3 fatty acids. Regular bathing using gentle, hydrating shampoos can also help prevent flaky or irritated skin. Additionally, probiotics and digestive enzymes added to your dog’s meals can promote healthy skin from the inside out. Some natural remedies like coconut oil, apple cider vinegar, and colloidal oatmeal applied topically can moisturize and soothe the skin. Always check with your vet before using any new supplements or topical treatments. Regular grooming, brushing, and skin checks are also important to catch any abnormalities early. Furthermore, flea, tick and parasite prevention helps avoid secondary infections that can worsen skin conditions. Lastly, limit baths to once every few weeks, use gentle shampoos, and avoid over-bathing which can strip the skin’s natural oils.