What is Black Fungus?
Black fungus spots on a dog’s skin are caused by a fungal infection. The medical term for this condition is dermatophytosis or “ringworm.” It is caused by fungi of the Microsporum, Trichophyton, or Epidermophyton genera. These fungi feed on keratin, the key protein that makes up hair, nails and the outer layer of skin.
The dark spots are a result of these fungi causing inflammation and altering pigment production. Melanin is produced at a higher rate in infected areas, leading to hyperpigmentation and the appearance of black spots.
While called “fungus,” dermatophytosis is not caused by the same fungi that cause issues like athlete’s foot in people. Dog fungal infections require treatment specifically for dogs to clear up the dark spots and treat the underlying fungal infection.
Types of Fungal Infections
Some of the most common fungal infections in dogs include:
Ringworm
Ringworm is caused by several fungal species in the genera Microsporum or Trichophyton. It affects the skin, hair, and nails. Symptoms include circular areas of hair loss, redness, itching, and scaling of the skin [1]. Ringworm is contagious and can spread between dogs and other animals. Treatment involves topical and/or oral antifungal medications like miconazole, ketoconazole, itraconazole, or terbinafine.
Yeast Infection
Yeast infections are caused by Malassezia species of yeast. They result in greasy skin, hyperpigmentation, hair loss, redness, itchiness, and a rancid odor. Treatment includes antifungal shampoos, topical miconazole or ketoconazole creams, and oral antifungal medications like itraconazole or fluconazole [2].
Aspergillosis
Aspergillosis is caused by Aspergillus fungi and affects the nose, sinuses, and sometimes the lungs and eyes. Symptoms include nasal discharge, nosebleeds, swelling of the face, and difficulty breathing. Treatment involves oral itraconazole and sometimes sinus flushes with antifungal solutions [1].
Causes & Risk Factors
Dogs can develop fungal infections in various ways. Fungi are everywhere in the environment, so dogs can be exposed through contact with soil, grass, plants, and decaying organic matter (https://www.merckvetmanual.com/dog-owners/disorders-affecting-multiple-body-systems-of-dogs/fungal-infections-in-dogs). Some fungal spores are also airborne. Dogs with weakened immune systems are more susceptible to developing fungal infections after exposure.
Certain breeds are at higher risk for fungal infections, including Shar Peis, Shih Tzus, Lhasa Apsos, and Pugs. These breeds have lots of skin folds where moisture and yeast can accumulate (https://www.vmsg-oc.com/site/blog/2021/01/29/fungal-infections-in-dogs-causes-symptoms-treatments).
Other factors that increase a dog’s risk of fungal infections include:
- Allergies or skin conditions causing inflamed skin
- Antibiotic use killing off healthy skin bacteria
- Endocrine disorders like hypothyroidism or Cushing’s disease
- Cancer or autoimmune disease
- Diabetes
- Obesity
- Diet lacking proper nutrition
Symptoms
The most common visible signs of fungal infections on a dog’s skin and coat include:
- Thickened, scaly, or flaky patches of skin
- Red, itchy skin (often circular patches)
- “Elephant skin” texture from thickened skin
- Hair loss or brittle, broken hairs
- Crusty sores or lesions
- Greasy skin with a rancid odor
- Darkened skin
- Pustules or papules
Changes to the skin and hair can range from mild flaking to major hair loss and thick calluses depending on the type and severity of infection. Skin may become extremely irritated, itchy, and inflamed.
Behavior changes can include increased scratching, licking, biting, or rubbing at affected areas. Dogs may seem restless or distressed by skin discomfort. Loss of appetite, lethargy, and depression are also possible if the infection is severe.
Diagnosis
Diagnose a black fungus infection is based on the vet’s clinical exam and diagnostic testing. The vet will examine the dog’s skin, looking for characteristic signs of fungal infection like scaling, redness, hair loss, and crusting. They will note the location and severity of lesions.
The vet may take skin scrapings or hair samples for fungal culture to identify the specific type of fungus causing infection. Fungal cultures allow sensitive identification of the fungal organism. Skin scrapings may also be examined under the microscope to look for telltale fungal hyphae (Source 1).
Blood tests may be recommended if the vet suspects systemic fungal infection. These can help identify elevated white blood cells and inflammation. Skin biopsies provide definitive diagnosis but are more invasive (Source 2).
Treatment
The most common treatment for fungal infections in dogs are antifungal medications. These can be administered topically or orally. Some commonly prescribed antifungal medications include:1
- Ketoconazole – An oral antifungal often prescribed for 2-4 weeks.
- Terbinafine – Another oral antifungal medication, usually prescribed for 2-8 weeks.
- Miconazole – A topical antifungal medication, applied directly to affected areas.
- Clotrimazole – Another topical antifungal cream or solution.
The course of treatment depends on factors like the type of fungus, severity of infection, and response to medication. Topical antifungals may be prescribed for 2-4 weeks. Oral medications often need to be given for a minimum of 2 weeks and sometimes for 2-3 months for more stubborn infections.2
In addition to medication, keeping the skin clean and dry can help clear up fungal infections. Your vet may recommend medicated antifungal shampoos as part of the treatment regimen.
1 https://vcahospitals.com/know-your-pet/yeast-dermatitis-in-dogs
2 https://www.vscot.com/site/blog/2020/12/03/diagnose-treat-fungal-infections-in-dogs
Home Remedies
There are several natural home remedies that can help treat fungal infections in dogs when used in conjunction with veterinary care and antifungal medications. Some options include:
Natural Antifungals
Certain natural substances have antifungal properties that can help fight fungal overgrowth when applied topically or given orally. These include:
- Coconut oil – Contains lauric acid with antifungal effects. Can be given orally or applied topically.
- Apple cider vinegar – Creates an unfavorable environment for fungus. Dilute and apply topically or add to food.
- Oregano oil – Has antifungal and antibacterial effects. Must be diluted before use.
Diet Changes
Eliminating sugars, carbohydrates, and allergens from the diet can help reduce fungus growth. Your vet may recommend a temporary elimination diet or hypoallergenic diet.
Topical Solutions
In addition to natural antifungals, there are other topical solutions that can be used on affected areas of the skin, such as:
- Antifungal shampoos containing chlorhexidine, miconazole, or ketoconazole
- Diluted vinegar or iodine soaks for the feet/pads
- Tea tree oil – Has antifungal properties when diluted
It’s important to consult your vet before using any home remedies. Proper diagnosis, treatment monitoring, and follow-up are essential when treating fungal infections.
Prevention
There are several steps dog owners can take to help prevent fungal infections in their pets:
Grooming and Hygiene: Regular bathing and grooming can help prevent fungal growth by removing dead skin cells, debris, and excess oils from your dog’s coat. Be sure to thoroughly dry your dog after baths. Trimming hair around moist areas like the muzzle, paws, and privates can also help decrease fungal growth.
Avoid Standing Water: Stagnant water provides the perfect breeding ground for fungus. Avoid letting your dog play or drink from standing water sources. After walks in damp areas, thoroughly dry your dog’s paws and belly.
Boost Immune Health: A strong immune system helps your dog fend off fungal infections. Feed a high-quality diet, avoid unnecessary medications/toxins, and minimize stress to support overall wellbeing. Supplements like fish oil and probiotics may also help.
If you notice any signs of a fungal skin infection in your dog, contact your veterinarian right away for proper diagnosis and treatment.
When to See a Vet
In some cases, home treatment may not be enough to resolve a fungal skin infection in dogs. It’s important to contact your veterinarian if:
- The infection is severe with widespread lesions or hair loss
- There is no improvement within 2-3 weeks of home treatment
- Signs of secondary infection develop, such as pus, worsening inflammation, or fever
A vet can provide prescription antifungal medication, antibiotic therapy if bacteria is present, medicated shampoos, or other treatments to clear up stubborn fungal infections. They can also do skin scrapings or cultures to identify the exact type of fungus involved.
Left untreated, some fungal infections can spread and cause greater harm to a dog’s skin and health. Seeking prompt veterinary care is advised if over-the-counter remedies do not resolve symptoms. With medications and proper follow-up care, most fungal skin conditions can be cured.
Outlook and Prognosis
The prognosis for black fungus in dogs is generally good when treated early and aggressively. However, the outlook depends on the severity and type of fungal infection.
Most cases of superficial fungal infections like ringworm or yeast resolve within 4-8 weeks with appropriate topical and/or oral antifungal treatment. Dogs should show improvement within 2-4 weeks. It is important to continue medication for the full course as prescribed by your veterinarian, even if symptoms resolve, to prevent recurrence.
More serious systemic or internal fungal infections can take months to fully resolve. Your veterinarian will monitor blood work and symptoms to determine when to discontinue medication. Relapses are possible if antifungal therapy is stopped too soon.
Without treatment, some fungal infections can spread and become life-threatening. However, even serious infections often resolve with aggressive antifungal treatment, especially when caught early.
Possible long-term effects of fungal infections in dogs include permanent hair loss, thickening of the skin or ears, and chronic yeast or fungal recurrence. Secondary skin infections may also develop. Lifelong antifungal therapy may be needed in some cases.
Overall, the majority of dogs make a full recovery and lead normal lives after antifungal treatment. Close monitoring, follow-up care, and prevention help ensure the best outcome.