Pimples and Pustules on Dogs: Causes and Treatment Guide

By Emiel Maddens  ·  Reviewed in consultation with licensed veterinary professionals  ·  Updated June 2026  ·  10 min read

Photo by Anya Prygunova on Unsplash

Discovering small, raised, pus-filled bumps on your dog's skin can be unsettling, especially if they appear suddenly or in large numbers. These lesions, known as pustules in veterinary terminology, are among the most common dermatological findings in dogs and represent one of the hallmark signs of bacterial skin infection. While they may look similar to human pimples or acne, the causes and implications of pustules on dogs are quite different from their human counterparts, and understanding these differences is important for getting the right treatment.

Pustules on dogs are almost always a sign that something else is going on beneath the surface. Unlike humans, where acne is primarily driven by hormonal changes and sebaceous gland blockage, dog pustules develop when bacteria, most commonly Staphylococcus pseudintermedius, invade damaged or inflamed skin and trigger an immune response. The underlying damage can come from allergies, parasites, hormonal disorders, or immune dysfunction, and identifying this root cause is essential for preventing the pustules from recurring after antibiotic treatment.

This comprehensive guide covers the different types of pustular conditions in dogs, from common bacterial folliculitis to rare autoimmune diseases, explains how veterinarians diagnose the cause, and reviews current treatment recommendations. Whether your dog has a few scattered bumps on their belly or widespread pustules across the body, this article will help you understand what you are seeing and what needs to happen next.

What Are Pustules and How Do They Form?

A pustule is a small, circumscribed elevation of the skin filled with purulent material, commonly known as pus. Pus is not simply bacteria; it is a mixture of dead neutrophils (white blood cells that fight infection), dead and living bacteria, tissue debris, and serum. When bacteria invade the skin, the immune system sends large numbers of neutrophils to the site to engulf and kill the invaders. The accumulation of these neutrophils, along with the bacteria they have killed and cellular debris from the battle, creates the visible pus-filled bump.

Follicular vs. Non-Follicular Pustules

Pustules in dogs can be classified based on their relationship to hair follicles. Follicular pustules develop within hair follicles and are the hallmark of bacterial folliculitis, the most common form of pyoderma in dogs. These pustules are typically small, centered around a hair shaft, and surrounded by a ring of redness. Non-follicular pustules develop in the epidermis between hair follicles and are seen in conditions such as impetigo and certain autoimmune diseases. Distinguishing between these two types helps guide the diagnostic approach and treatment plan.

The lifecycle of a typical bacterial pustule begins with bacterial colonization of damaged skin, progresses through an acute inflammatory response with neutrophil recruitment, reaches its peak as a visible pus-filled bump, and then resolves either through rupture (releasing the contents onto the skin surface) or through gradual reabsorption. When a follicular pustule ruptures, it often leaves behind a characteristic circular pattern called an epidermal collarette, a ring of peeling skin surrounding a central area of hyperpigmentation. These collarettes are among the most recognizable signs of resolving pyoderma in dogs.

It is important to understand that the formation of pustules represents an active immune response to infection. The immune system is doing exactly what it should be doing by sending neutrophils to fight the bacteria. The problem lies not with the immune response itself but with the conditions that allowed the bacteria to invade in the first place. This is why treatment must address both the infection and the underlying predisposing factor.

Superficial Bacterial Pyoderma

The Most Common Cause of Dog Pustules

Superficial bacterial pyoderma, specifically superficial bacterial folliculitis, is by far the most common cause of pustules on dogs. Staphylococcus pseudintermedius, a bacterium that normally lives harmlessly on healthy dog skin as part of the normal microbiome, is the primary pathogen responsible for over 90% of canine pyoderma cases. Under normal circumstances, the skin's barrier function, local immune defenses, and competitive pressure from other microorganisms keep Staphylococcus populations in check. When these protective mechanisms are compromised by allergies, hormonal disorders, immune suppression, or skin barrier damage, Staphylococcus can overgrow and invade, triggering the pustular response.

Clinical Appearance

Superficial pyoderma presents with small, fragile pustules that are often centered on hair follicles. These pustules are typically less than one centimeter in diameter and contain creamy white to yellowish pus. Because canine pustules are very fragile and rupture easily, owners often do not see intact pustules but instead notice the secondary lesions they leave behind. Epidermal collarettes, circular rings of peeling skin, are particularly common and can be the most visible sign of resolving pyoderma. Other secondary lesions include areas of hyperpigmentation (darkened skin), patches of hair loss, and honey-colored crusts where pustular contents have dried on the skin surface.

Distribution Patterns

The distribution of pustules provides important clues about the underlying cause. Pustules on the ventral abdomen (belly), inner thighs, and groin are the classic presentation of superficial pyoderma and are common in dogs with allergies. Pustules concentrated on the dorsal trunk (back) and flanks may suggest folliculitis secondary to flea allergy or contact with environmental allergens. Pustules on the chin and muzzle can occur in canine acne, particularly in short-coated breeds. Generalized pustules covering multiple body regions suggest more widespread immune compromise or severe allergic disease.

It bears emphasizing that superficial bacterial pyoderma is almost never a primary disease. In the vast majority of cases, there is an underlying condition that has allowed the normally harmless skin bacteria to become pathogenic. Treating the pyoderma with antibiotics alone, without addressing the underlying trigger, will result in the infection returning once antibiotics are discontinued. This cycle of treatment and recurrence is one of the most common and frustrating patterns seen in veterinary dermatology.

Pustules on dogs are typically caused by bacterial infection of the hair follicles and respond well to targeted treatment.

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Puppy Impetigo and Canine Acne

Puppy Impetigo

Impetigo is a superficial bacterial skin infection that is particularly common in puppies, typically between two and six months of age. Unlike folliculitis, impetigo involves non-follicular pustules that develop on the relatively hairless skin of the ventral abdomen and inner thighs. The pustules of impetigo tend to be larger and more superficial than those of folliculitis, and they rupture easily to leave thin, honey-colored crusts. Puppy impetigo is generally considered a mild, self-limiting condition associated with the immature immune system of young dogs, poor hygiene conditions, or concurrent illness. It typically responds well to topical antiseptic treatment with chlorhexidine and rarely requires systemic antibiotics.

Canine Acne

Canine chin acne, technically known as canine muzzle folliculitis and furunculosis, is a condition primarily affecting short-coated breeds such as Boxers, Bulldogs, Great Danes, Doberman Pinschers, and Rottweilers. It presents as papules, pustules, and sometimes deeper, draining nodules on the chin, lips, and muzzle. Unlike human acne, which is driven by hormonal changes and sebaceous gland blockage, canine chin acne is thought to be caused by hair follicle trauma from the short, coarse hairs of the chin being pushed back into the follicle during activities like eating from bowls or rubbing the face on surfaces. This follicular trauma allows bacteria to invade, producing the characteristic pustular lesions.

Treatment for mild canine acne typically involves daily topical cleansing with chlorhexidine or benzoyl peroxide wipes or washes. Switching from plastic food and water bowls to ceramic or stainless steel bowls can help, as plastic bowls can harbor bacteria in microscopic scratches and may cause contact irritation. Moderate to severe cases with deep nodules or draining tracts may require systemic antibiotics and, in some cases, topical or systemic retinoids. Most dogs with chin acne respond well to treatment, though some individuals require long-term topical maintenance to prevent recurrence.

Deep Pyoderma: When Infection Goes Deeper

While superficial pyoderma involves the epidermis and the superficial portion of hair follicles, deep pyoderma extends into the deeper layers of the skin, including the dermis and sometimes the subcutaneous tissue. Deep pyoderma is a more serious condition that produces larger, more painful lesions including deep-seated pustules, nodules, draining tracts (fistulae), and areas of tissue necrosis. The most common form of deep pyoderma is deep bacterial folliculitis and furunculosis, where infected hair follicles rupture beneath the skin surface, releasing hair shaft fragments, bacteria, and inflammatory material into the surrounding dermis.

The release of foreign material (hair fragments) and bacteria into the dermis triggers an intense inflammatory response that produces deep, firm, often painful nodules that may drain thick, purulent or serosanguineous fluid. These deep infections are significantly more difficult to treat than superficial pyoderma, requiring longer courses of systemic antibiotics (typically four to six weeks or more, extending two weeks past clinical resolution) and more intensive topical therapy. Culture and sensitivity testing is strongly recommended for deep pyoderma to ensure the chosen antibiotic is effective against the specific bacteria involved.

German Shepherd Deep Pyoderma

German Shepherds are predisposed to a particularly severe form of deep pyoderma that can affect the trunk, flanks, and thighs. This breed-associated deep pyoderma is often recurrent and may be related to an underlying immunodeficiency specific to the breed. Affected dogs develop multiple draining tracts, nodules, and areas of deep infection that can be very difficult to control. Long-term management with regular medicated bathing, intermittent antibiotic courses guided by culture results, and investigation for underlying triggers (particularly allergies) is typically necessary.

Interdigital furunculosis, a specific form of deep pyoderma affecting the skin between the toes, is another common presentation. Dogs develop painful, swollen, draining nodules between their toes that cause lameness and significant discomfort. The condition is often driven by a combination of allergic inflammation, conformational factors (tight, webbed interdigital spaces), and secondary bacterial infection. Treatment requires both antibiotic therapy for the infection and management of the underlying allergic or conformational triggers.

Autoimmune Pustular Diseases

Pemphigus Foliaceus

Pemphigus foliaceus is the most common autoimmune skin disease in dogs and is an important differential diagnosis for pustular conditions because it requires fundamentally different treatment than infectious pyoderma. In pemphigus foliaceus, the immune system produces antibodies that attack desmoglein-1, a protein that holds epidermal cells together. This autoimmune attack causes the epidermal cells to separate from each other (a process called acantholysis), forming large, fragile pustules filled with acantholytic cells rather than bacteria. The pustules of pemphigus typically appear on the face, nose, ears, and footpads, though they can become generalized.

Pemphigus pustules look clinically similar to infectious pustules, which is why cytological examination is critical. Cytology of a pemphigus pustule reveals acantholytic keratinocytes, which are rounded, dark-staining epidermal cells that have lost their connections to neighboring cells, floating among neutrophils. Bacteria are typically absent or present in very low numbers. This cytological finding is highly suggestive of pemphigus and prompts skin biopsy for definitive diagnosis. Treatment of pemphigus foliaceus involves immunosuppressive medications, most commonly prednisone combined with azathioprine or mycophenolate, to suppress the autoimmune attack on the skin.

Sterile Pustular Conditions

Several other immune-mediated conditions can produce sterile (non-infectious) pustules on dog skin. Sterile eosinophilic pustulosis produces pustules filled with eosinophils (a type of white blood cell associated with allergic and parasitic responses) rather than neutrophils. Subcorneal pustular dermatosis produces superficial, non-follicular pustules that tend to affect the trunk and head. Drug reactions can occasionally produce pustular eruptions. These conditions are relatively rare compared to infectious pyoderma but are important to consider when pustules do not respond to antibiotic treatment, as they require immunomodulatory therapy rather than antimicrobials.

Diagnosing Pustular Conditions in Dogs

Cytology: The Essential First Test

Cytology is the single most important diagnostic test for evaluating pustules on dogs and should be performed on virtually every case. The technique involves carefully rupturing an intact pustule with a sterile needle and pressing a microscope slide against the expressed material, or gently touching the slide to the surface of a freshly ruptured pustule. After staining, the slide is examined under the microscope to identify the cell types and organisms present. The presence of large numbers of cocci (round bacteria) phagocytized by neutrophils confirms bacterial pyoderma. Acantholytic keratinocytes among neutrophils suggest pemphigus. Predominantly eosinophilic infiltrates point toward sterile eosinophilic pustulosis or parasitic disease.

Culture and Sensitivity

Bacterial culture and sensitivity testing is recommended for cases of deep pyoderma, recurrent pyoderma that has been treated with antibiotics multiple times, cases that fail to respond to empirical antibiotic therapy, and whenever rod-shaped bacteria (rather than cocci) are seen on cytology. The test identifies the specific bacterial species involved and determines which antibiotics will be effective against it. This is particularly important given the increasing prevalence of methicillin-resistant Staphylococcus pseudintermedius (MRSP), which requires specific antibiotic choices based on sensitivity results rather than empirical therapy.

Identifying the Underlying Cause

Beyond diagnosing the pustular condition itself, determining the underlying trigger is essential for long-term management. Skin scrapes rule out parasitic causes. Blood work screens for hormonal disorders. Diet trials evaluate for food allergy. Allergy testing identifies environmental allergens. Skin biopsy is performed when autoimmune disease is suspected or the diagnosis is uncertain. The goal is to answer not just 'what type of pustules does this dog have?' but 'why is this dog developing pustules in the first place?'

Treatment of Pustular Skin Conditions

Topical Therapy

Topical antimicrobial therapy is an important component of treating bacterial pustules, and for mild, localized infections, it may be sufficient as the sole treatment. Chlorhexidine-based products, including sprays, wipes, and shampoos, are widely used for their broad-spectrum antibacterial and antifungal activity. Medicated shampoos should be left on the skin for ten to fifteen minutes before rinsing to allow adequate contact time. Benzoyl peroxide shampoos have the added benefit of flushing hair follicles and are particularly useful for follicular pyoderma. Topical mupirocin ointment can be applied to individual lesions for targeted treatment. Using topical therapy alongside systemic antibiotics can shorten the required treatment course and reduce the overall antibiotic exposure.

Systemic Antibiotics

Moderate to severe or widespread bacterial pyoderma requires systemic antibiotic therapy. First-line antibiotics for uncomplicated superficial pyoderma include cephalexin, amoxicillin-clavulanate, and clindamycin. Treatment should continue for a minimum of three to four weeks and should extend at least one week beyond complete clinical resolution of all lesions. Premature discontinuation of antibiotics is a common cause of relapse and contributes to antibiotic resistance. For deep pyoderma, longer courses of six to eight weeks are typical. Culture-guided antibiotic selection is recommended for recurrent, deep, or non-responsive cases.

Treating Underlying Conditions

Addressing the underlying cause is the single most important factor in preventing recurrence of pustular skin conditions. Dogs with allergy-driven pyoderma need long-term allergy management through immunotherapy, anti-itch medications, or dietary modification. Hormonal disorders require appropriate endocrine therapy. Immune-mediated pustular diseases need immunosuppressive medication. Without addressing the root cause, pustules will almost invariably recur once antibiotics are discontinued, leading to frustrating cycles of treatment and relapse and increasing the risk of developing antibiotic-resistant infections.

Antibiotic stewardship is an increasingly important consideration in veterinary dermatology. The emergence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) has made responsible antibiotic use more critical than ever. Strategies to minimize unnecessary antibiotic exposure include maximizing the use of topical therapy, always completing the full prescribed antibiotic course, using culture and sensitivity to select the narrowest-spectrum effective antibiotic, and focusing on long-term management of underlying conditions to prevent recurrence.

Pimples and Pustules on Dogs FAQ

Q: Can I pop my dog's pimples?

No, you should not attempt to pop or squeeze pustules on your dog's skin. Manually expressing pustules can force infectious material deeper into the skin, potentially converting a superficial infection into a deep one. It also causes pain and tissue trauma that delays healing and creates opportunities for additional bacterial invasion. If your veterinarian needs to collect material from a pustule for diagnostic testing, they will do so with sterile technique. At home, the best approach is to keep the affected area clean with a veterinary-approved antiseptic wash and to seek professional evaluation for appropriate treatment.

Q: Are dog pimples contagious to humans?

Staphylococcus pseudintermedius, the bacterium responsible for most canine pyoderma, is considered primarily a dog-adapted species and rarely causes infection in healthy humans. However, it can occasionally be transmitted to humans, particularly those who are immunocompromised, elderly, or have skin wounds. The risk of transmission is low, but basic hygiene measures such as washing your hands after touching your dog's lesions are sensible precautions. Methicillin-resistant strains (MRSP) are of greater concern from a public health perspective, though clinical infections in humans remain uncommon.

Q: Why do my dog's pimples keep coming back?

Recurrent pustules are one of the most common problems in veterinary dermatology, and they almost always indicate an underlying condition that has not been adequately addressed. The most common underlying causes are allergic skin disease (atopic dermatitis, food allergy, flea allergy), hormonal disorders (hypothyroidism, Cushing's disease), and immune dysfunction. Each episode of antibiotic treatment clears the current infection, but without treating the underlying cause, the conditions that allow bacteria to invade the skin remain, and new infections develop. A thorough diagnostic workup to identify and manage the underlying trigger is the key to breaking the cycle.

Q: What is the difference between dog pimples and an allergic reaction?

Dog pimples (pustules) are the visible result of bacterial infection in the skin, while an allergic reaction is an immune-mediated inflammatory response to an allergen. However, the two are closely connected because allergic skin disease is the most common underlying cause of bacterial pyoderma in dogs. Allergic inflammation damages the skin barrier, alters the local immune environment, and creates conditions that allow bacteria to invade and form pustules. So in many cases, the pustules are both a sign of bacterial infection and an indirect sign of allergic disease.

Q: How can I tell if my puppy's belly bumps are normal?

Small, scattered pustules on the relatively hairless belly skin of young puppies (two to six months of age) are often puppy impetigo, a common, usually mild superficial bacterial infection. Puppy impetigo typically presents as small, thin-walled pustules that rupture easily and leave behind honey-colored crusts. The puppy is usually otherwise healthy and the bumps do not seem to cause significant discomfort. Mild cases often resolve with topical chlorhexidine cleansing. However, if the pustules are numerous, spreading rapidly, accompanied by fever or lethargy, or if the puppy appears unwell, veterinary evaluation is recommended to rule out more serious conditions.

Q: Do dog pimples need antibiotics?

Not all pustular conditions require antibiotics. Mild, localized infections such as puppy impetigo or a few scattered follicular pustules may respond to topical antiseptic treatment alone. Autoimmune pustular conditions like pemphigus require immunosuppressive therapy, not antibiotics. However, moderate to severe bacterial pyoderma, deep pyoderma, and widespread infections do require systemic antibiotics for resolution. Your veterinarian will determine the most appropriate treatment based on the type, severity, and extent of the pustular condition, and whether underlying causes need to be addressed concurrently.

Sources

Bajwa, J. (2017). Canine superficial pyoderma and therapeutic considerations. Canadian Veterinary Journal, 58(12), 1287-1291.

Hillier, A., Lloyd, D.H., Weese, J.S., et al. (2014). Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis. Veterinary Dermatology, 25(3), 163-175.

Bloom, P. (2014). Canine superficial bacterial folliculitis: current understanding of its etiology, diagnosis and treatment. Veterinary Journal, 199(2), 217-222.

Olivry, T. & Linder, K.E. (2009). Dermatoses affecting desmosomes in animals: a mechanistic review of acantholytic blistering skin diseases. Veterinary Dermatology, 20(5-6), 313-326.

Morris, D.O., Loeffler, A., Davis, M.F., et al. (2017). Recommendations for approaches to methicillin-resistant staphylococcal infections of small animals. Journal of the American Veterinary Medical Association, 251(8), 954-965.

Miller, W.H., Griffin, C.E., & Campbell, K.L. (2013). Muller and Kirk's Small Animal Dermatology, 7th Edition. Elsevier.

Related Reading

• Pyoderma in Dogs, Complete guide to bacterial skin infections
• Chlorhexidine for Dogs, How antiseptic sprays help manage skin infections
• Hot Spots in Dogs, Understanding acute moist dermatitis
• Allergy Testing in Dogs, Finding the root cause of recurring infections

Emiel Maddens

Founder of Vetified. Develops topical antifungal and antimicrobial formulations for companion animals. Vetified products are listed on DailyMed and manufactured through FDA-registered facilities in the United States.