If you notice angry red bumps, swelling, or even open sores on your dog's paws, face, or where they lick excessively, it could be furunculosis. This deep bacterial infection goes beyond just a simple skin issue. The main types of furunculosis in dogs include interdigital (between the toes), post-grooming, muzzle or facial ("hot spots"), and anal furunculosis. Certainly, any type can make your dog miserable but don't worry while furunculosis can be concerning, understanding the causes and working with your veterinarian are the keys to giving your dog relief.

What is furunculosis in dogs?

Furunculosis isn't your average skin irritation. Think of it like a severe, deep-rooted infection within the deeper skin layers. This stubborn bacterial infection often causes:

  • Red, swollen bumps or blisters
  • Pain, itchiness, or licking of the affected area
  • Draining pus or crusty sores
  • Hair loss around the affected site

Types of furunculosis in dogs

Furunculosis can pop up in various areas on your dog's body, leading to specific types:

  1. Interdigital furunculosis: Affects the sensitive skin between your dog's toes.
  2. Muzzle or facial furunculosis: Appears around the muzzle, chin, or face.
  3. Acral lick dermatitis (lick granuloma): Often starts as a minor irritation that your dog worsens by constant licking. Usually affects the wrists (carpus) or ankle (tarsus) regions.
  4. Post-grooming furunculosis: Develops shortly after grooming or clipping.
  5. Anal furunculosis: A painful infection around the anus, sometimes causing draining sores.

In this article, we will discuss each type of furunculosis in more detail and explore potential causes and treatment options. Remember, if you notice any signs or symptoms of furunculosis on your dog, it's important to consult with your veterinarian for proper diagnosis and treatment.

1. Interdigital furunculosis in dogs

Interdigital furunculosis, also known as interdigital cysts or pododermatitis, is a common type of furunculosis that affects the paws and toes of dogs.

Causes and risk factors

  1. Allergies: When your dog has allergies, their skin becomes inflamed and irritated. This creates a welcoming environment for bacteria or yeast to overgrow, leading to infection and furunculosis.
  2. Conformation and hair: Dogs with short, bristly hair on their paws or excess webbing between their toes may experience friction and micro-injury, which can break down the skin barrier. This allows bacteria to get in.
  3. Foreign material: Pieces of grass, dirt, thorns, or other objects that get lodged between your dog's toes can cause irritation and punctures, opening the door to bacterial infection.
  4. Immune system defects: Sometimes, a dog's immune system struggles to fight off even normal skin bacteria, which can lead to opportunistic infections like furunculosis.
  5. Underlying conditions: Diseases like hypothyroidism or Cushing's disease can make a dog's skin generally more vulnerable to infections.
  6. Breed-related: Certain breeds, such as Bulldogs and Labrador Retrievers, are more prone to interdigital furunculosis due to their genetics and anatomical confirmations.

Symptoms of interdigital furunculosis in dogs

If you notice your dog suddenly become fixated on its paws, it's time to take a closer look. Interdigital furunculosis can make those paws feel painful and itchy. Look out for these signs:

  • Red, swollen paws in general, or between specific toes
  • Licking or chewing the feet
  • Limping or avoiding putting weight on the affected paw
  • A foul odor coming from the affected area
  • Bumps, blisters, or open sores

If you notice any of these symptoms, it's important to have your dog examined by your veterinarian. Early detection and treatment can prevent the condition from worsening and causing more harm than good.

Treatment options for interdigital furunculosis

The treatment plan for interdigital furunculosis will depend on the underlying cause and severity of the infection.

In most cases, your veterinarian will prescribe antibiotics to fight off the bacterial infection. Antibiotics are often required for many weeks, sometimes up to 12-16 weeks in severe cases. The type of antibiotic used will often depend on the results of a bacterial culture and sensitivity test.

As concurrent fungal infections are often present, treatment with appropriate antifungal therapy is often warranted. Your vet can determine if there is a fungal component by performing skin cytology.

Your veterinarian may also recommend medicated paw soaks to reduce inflammation and promote healing. These soaks typically involve a warm antiseptic solution where your dog's paws rest for a prescribed amount of time. They can be surprisingly soothing, reducing redness and discomfort.

In addition, your veterinarian might prescribe topical creams or sprays formulated to specifically address your dog's furunculosis.

Can interdigital furunculosis in dogs be prevented and what is the prognosis?

For any treatment plan to be successful, addressing the underlying cause is always important.

If your dog has allergies or other underlying issues contributing to the furunculosis, your veterinarian will develop a long-term management plan. This might include special diets, allergy medication, or other treatments.

Interdigital furunculosis can be challenging to manage, but most dogs respond well to proper treatment.

I recommend rechecking every 2-3 weeks after starting a treatment plan, to monitor progress and make any necessary adjustments.

2. Muzzle or facial furunculosis in dogs

This form of furunculosis targets the skin on your dog's muzzle, lips, and chin and occurs when there is a deep, severe infection around the hair follicle. Typically, dogs develop lesions between the ages of 6 and 12 months, which may continue into adulthood.

Additionally, we can also include the common "hot spots" or acute moist dermatitis in this category as well, as this is a form of facial furunculosis in dogs.

Potential causes of facial furunculosis in dogs

While the exact cause isn't always clear, here's what we know:

  1. Rough play or chin rubbing: If your dog loves roughhousing or frequently rubs their chin on things, it might damage the short hairs on their muzzle. Damaged hairs can get pushed under the skin, causing irritation and setting the stage for infection.
  2. Short-coated breeds: This condition is much more common in dogs with short, coarse fur.
  3. Secondary infection: Sometimes, the furunculosis starts with a minor injury that then becomes infected with bacteria.

Signs and symptoms of facial furunculosis in dogs

Early signs can include small, hairless bumps (papules) appear first. Later, these bumps can become enlarged pimples (pustules) and may develop into open sores.

Your dog might also show mild itchiness of the muzzle. However, if there's a deep bacterial infection beneath the skin, the area can be painful.

The lower lips and skin around the mouth can also be affected. Unlike other deep skin infections, lesions will only occur on the face.

facial furunculosis in dogs
A "hot spot" is an example of furunculosis in dogs

What is the treatment for muzzle or facial furunculosis?

Having your dog diagnosed by a veterinarian is essential. Your vet may first want to biopsy the affected area(s) to rule out conditions like demodicosis (mites).

Treatment will depend on the severity of the furunculosis but might include:

Targeted skin treatment:

  • Medicated cleansers or washes to reduce bacteria and inflammation.
  • Topical antibiotics (e.g. mupiricin) or antifungal creams are applied directly to affected areas.
  • Excessive use of these products may lead to further irritation and inflammation

Systemic treatment:

  • Oral antibiotics for more severe or widespread infections.
  • In some cases, anti-inflammatory medication might be needed for pain or swelling.

Preventing recurrence:

  • If your dog is prone to chin rubbing, try to discourage rough play or abrasive surfaces.
  • For acne-prone dogs, your vet might recommend ongoing medicated washes.
  • In cases with scarring due to past deep infections, the affected areas might, unfortunately, be prone to recurring infections. There is no specific treatment for the scarring itself.

3. Acral lick dermatitis (lick granuloma)

Acral lick dermatitis or lick granuloma is another common type of furunculosis in dogs. This type of furunculosis often starts as a minor irritation – an itchy spot, a bug bite, or a small cut. However, your dog's constant licking worsens the problem, creating a frustrating cycle.

What are the causes of acral lick furunculosis (lick granuloma) in dogs?

Acral lick dermatitis isn't simple. It often starts with something making your dog itchy or uncomfortable, including:

  1. Allergies: Food allergies, allergies to things in the environment (atopy), or flea allergies can all lead to itchy skin.
  2. Pain: injuries, arthritis pain, nerve problems, or even something stuck in the paw can trigger focused licking.
  3. Infections: Skin infections, like mites (demodicosis) or fungal infections, can be a culprit.
  4. Behavioral issues: Boredom, anxiety, or a compulsive disorder can cause some dogs to fixate on licking one spot.

No matter what the original trigger is, the constant licking creates a vicious cycle. It damages the skin, making it itchier and more prone to infection, leading to even more licking.

What are the symptoms of acral lick furunculosis (lick granuloma)?

Dogs with a lick granuloma often have a well-defined, hairless patch (plaque) with clear borders, unlike a more general skin irritation.

The skin surface might be red, thickened, cracked, or even have open sores in advanced cases. The most common location is the lower part of the front legs, but it can occur anywhere your dog can easily reach for licking.

The constant, obsessive licking of the affected spot is a hallmark of this condition.

tarsus lick granuloma
Lick granuloma on the ankle (tarsus) of a dog

What is the treatment for acral lick furunculosis in dogs?

Treating acral lick dermatitis requires patience and a multi-pronged approach. Since there are often several factors involved, your veterinarian is your best resource! Treatment focuses on:

  1. Breaking the itch-lick cycle: This is very important for healing and can involve:
    1. Temporary licking prevention: E-collars, bandages, anti-lick sprays, etc., might be needed initially.
    2. Addressing the itch: Treating the underlying cause, whether it's allergies, infection, or pain, reduces licking motivation.
  2. Wound care: If the lick granuloma is open or infected, your vet may prescribe medications or special cleaning techniques.
  3. Behavioral management: Especially for compulsive lickers, this is essential for long-term success. That might involve:
    1. Environmental enrichment: Reducing boredom, providing mental stimulation.
    2. Anxiety management: Medication or behavior training to help stressed dogs.
    3. Specialized training: Working with a dog trainer to redirect obsessive licking.

Prognosis and preventative strategies

Acral lick dermatitis requires patience and commitment from both you and your vet. It's important to understand that treatment can take a few months, and even with quick initial improvement, complete resolution might be gradual. Even after successful treatment, it's possible for new lesions to appear, especially if the initial trigger for the licking wasn't fully addressed.

Prevention of future lick granulomas often depends on the root cause. If your dog has an underlying behavioral issue, behavior modification training and environmental enrichment (more playtime, walks, puzzle toys, etc.) can help change the licking habit. If allergies are the culprit, your veterinarian will work with you to manage them, which might include special diets or medication to reduce flare-ups.

4. Post-grooming furunculosis in dogs

Post-grooming furunculosis is a common issue only in dogs. It shows up as bumps, sores, and boils on the back within a day or two after grooming, especially where the clipper was used, causing a lot of pain for your dog.

After grooming, furunculosis can happen in any breed, but it's more common in short-coated dogs. Interestingly, German Shepherds and Labrador Retrievers are often affected.

Most cases of post-grooming furunculosis are due to an aggressive bacteria called Pseudomonas aeruginosa.

What are the causes of post-grooming furunculosis in dogs?

Post-grooming furunculosis can happen in a few ways:

  1. Rough grooming: Sometimes, grooming techniques that are vigorous (like back-brushing or hard scrubbing) can damage the delicate hair follicles, essentially creating tiny injuries in the skin. This opens the door for infection.
  2. Dirty supplies: If a groomer's tools, water, or products are contaminated with bacteria, this can be introduced to your dog's skin during their bath or haircut. This is especially risky if their skin is already slightly irritated from grooming.
  3. Sensitive dogs: Dogs already struggling with allergies or skin sensitivities have a weaker skin barrier and are more likely to develop an infection after grooming.

What are the symptoms of post-grooming furunculosis in dogs?

Post-grooming furunculosis usually appears quickly and dramatically:

  • Skin changes: Look for red bumps, pus-filled blisters, dark fluid-filled blisters that might drain, and raised patches of irritated skin. These often cover areas that were clipped or shaved.
  • Crusting: As sores heal, you may see brown or black crusts, like dried blood.
  • Location: Most common on the back, neck, and the lower back area. It can spread to the sides of your dog's body.
  • Pain and discomfort: Your dog might become lethargic, have a poor appetite, run a fever, and seem extremely sensitive to touch on their back.

Important note: These severe symptoms warrant an immediate vet visit. Post-grooming furunculosis can progress rapidly if left untreated.

What are the treatments for post-grooming furunculosis?

Post-grooming furunculosis requires urgent veterinary attention. Here's what you can expect:

To be successful with treatment, your veterinarian will take a swab of the affected area and send for a bacterial culture and sensitivity test. This test tells us what bacteria is causing the issue and which antibiotic is most effective.

As we wait for the results to come back, which can take a few days, we start your dog on antibiotics immediately to combat the infection. This treatment often needs to continue for several weeks, even after your dog seems better. The antibiotic may change depending on the results of the culture test.

As most cases are due to Pseudomonas aeruginosa, we typically start with a fluoroquinolone antibiotic such as enrofloxacin or marbofloxacin.

Post-grooming furunculosis is very painful and we need to prescribe pain medication to help keep your dog comfortable. These medications can include NSAIDs or corticosteroids, tramadol, and/or gabapentin.

What is the prognosis for post-grooming furunculosis?

The good news is that with prompt veterinary treatment and proper care at home, most dogs respond well to treatment for post-grooming furunculosis. Studies have shown that many dogs start to show significant improvement within a few weeks of starting the appropriate antibiotics.

However, it is important to complete the entire course of treatment as directed by your vet, even if your dog seems fully recovered before the medication is finished. This helps prevent the infection from returning and ensures complete healing, minimizing the risk of future grooming-related issues.

5. Anal furunculosis in dogs

Anal furunculosis, also known as perianal fistula, is a chronic inflammatory disease that affects the skin and tissues around the anus. This condition is not related to the anal glands or sacs.

Although it can occur in any breed, German Shepherds are most commonly affected with studies revealing more than 80% of all cases occur within the breed.

Furthermore, anal furunculosis occurs primarily in middle-aged dogs and is more common in intact males (unneutered males).

What are the causes of anal furunculosis in dogs?

The exact cause of anal furunculosis is unclear and may be multifactorial. We do suspect this disorder is an immune-mediated, or autoimmune condition.

What are the symptoms of anal furunculosis in dogs?

Anal furunculosis causes significant discomfort for your dog. Watch for these signs:

  • Difficulty defecating: This includes straining (tenesmus), painful pooping (dyschezia), or changes in their stool (constipation or diarrhea).
  • Licking or biting: Your dog might obsessively lick or chew at their rear end due to pain or itchiness. This can worsen the problem (self-mutilation).
  • Foul odor or discharge: You might notice an unpleasant smell, or see pus or blood coming from the area.
  • Tail changes: Some dogs hold their tail down unusually due to the pain.
  • Behavioral changes: The discomfort can lead to scooting on the floor, weight loss, or lethargy.
perianal furunculosis
Notice the inflammation and open sores in the perianal region

Important note: Initially, anal furunculosis might be hidden, especially in long-coated dogs. That's why regular inspection of this area is important, especially if your dog has risk factors.

What is the treatment for anal furunculosis in dogs?

The good news is that medical management has become the primary treatment approach for perianal fistulas, with surgery reserved for those cases where medications aren't successful. Here's how the current treatment works:

Two-Phase Medical Management:

  • Induction phase (First 4 Months): The goal is to get those painful fistulas under control. This involves immune-modulating medications, often at higher doses initially:
    • Cyclosporine: This medication helps calm down an overactive immune system thought to be behind the problem.
    • Tacrolimus: This topical medicine has a similar effect but is applied directly to the affected skin.
    • Steroids (If needed): Corticosteroids like prednisone offer potent relief but come with potential side effects, so they're used with caution.
  • Maintenance phase: Once your dog's doing better and in remission, the goal is preventing recurrences. This often means continuing medication long-term, possibly at a lower dose. I recommend regular check-ups during this phase.

During treatment, treating any secondary infections that are present is very important. Additionally, dogs with anal furunculosis should be evaluated for adverse food reactions and your vet may therefore recommend a specialized prescription diet for this purpose.

What is the prognosis for dogs with anal furunculosis?

Anal furunculosis is often a long-term challenge. With careful veterinary management, most dogs can see a significant improvement in their quality of life, even if a complete cure isn't always possible.

Be prepared for the possibility of lifelong medication and adjustments to your dog's care routine to help keep flare-ups at bay.

In conclusion, this article explored furunculosis in dogs, focusing on common types like interdigital furunculosis, muzzle furunculosis, acral lick dermatitis, post-grooming furunculosis, and anal furunculosis. Remember, while furunculosis can make your dog uncomfortable, there are treatments available. The prognosis varies depending on the type of furunculosis present, with some types being more manageable than others.

If you have any questions, please contact your veterinarian for personalized care for your dog.