Understanding Pyoderma
Pyoderma — from the Greek for "pus skin" — is a bacterial skin infection and one of the most frequent reasons dogs are brought to veterinary practices for dermatological complaints. In the vast majority of cases, the causative organism is Staphylococcus pseudintermedius, a bacterium that normally lives harmlessly on canine skin but becomes problematic when the skin's natural defences are disrupted. The severity of the disease depends on how deeply the infection has penetrated, which is why pyoderma is classified into three distinct categories.
Pyoderma is almost never a primary disease. It develops when something else has gone wrong — an underlying allergy, hormonal imbalance, parasitic infestation, anatomical abnormality, or immune system dysfunction. Identifying and addressing this underlying cause is as important as treating the infection itself, because without it, recurrence is nearly inevitable.
Surface Pyoderma
Surface pyoderma involves bacterial overgrowth on the skin surface without invasion into the skin itself. The classic presentations in this category are acute moist dermatitis — commonly called hot spots — and intertrigo, which occurs in skin folds.
Hot spots appear suddenly, often within hours. They are intensely itchy, moist, red, and rapidly expanding areas of skin inflammation. Dogs will chew and scratch at the area relentlessly, creating a self-perpetuating cycle of damage and worsening infection. Common trigger sites include the cheeks, neck, and hip area, particularly in dogs with thick or dense coats that retain moisture. Golden Retrievers and Labradors are disproportionately affected.
Skin fold intertrigo occurs wherever skin folds trap warmth, moisture, and bacteria — facial folds in Bulldogs and Pugs, lip folds, vulvar folds, and tail folds are all vulnerable. The skin within these pockets becomes macerated, malodorous, and inflamed. Management requires both treating the acute infection and, in many cases, keeping the folds clean and dry on an ongoing basis.
Treatment of surface pyoderma is typically topical: antimicrobial shampoos, sprays, and wipes containing chlorhexidine or benzoyl peroxide, combined with clipping of the hair around affected areas to allow air circulation and facilitate treatment. Systemic antibiotics are not usually required for true surface infections caught early.
Superficial Pyoderma
Superficial pyoderma is the most common form encountered in practice. The infection extends into the epidermis and follicles but does not yet penetrate the deeper dermis or subcutaneous tissues. Two main presentations occur: impetigo and superficial folliculitis.
Impetigo predominantly affects puppies. Small, fluid-filled pustules develop on the relatively hairless skin of the abdomen and groin, typically without significant pruritus. The pustules rupture easily, leaving behind small epidermal collarettes — circular, scaly rings that are a hallmark of superficial bacterial infection. Most cases in healthy puppies resolve with topical therapy alone, though stress, nutritional deficiency, or intercurrent illness can perpetuate infection.
Superficial folliculitis involves infection of hair follicles and is the most commonly encountered presentation of pyoderma in adult dogs. Lesions include small pustules around hair follicles, papules, crusts, epidermal collarettes, and in short-coated breeds, a characteristic "moth-eaten" pattern of partial hair loss. Pruritus is variable. The condition is strongly associated with underlying allergic skin disease, particularly atopic dermatitis and food allergy, as well as with demodicosis and hormonal conditions such as hypothyroidism.
Systemic antibiotics are frequently required for superficial folliculitis, particularly when lesions are widespread. First-line choices should be guided by culture and sensitivity testing where possible, given increasing concerns about methicillin-resistant Staphylococcus pseudintermedius. Clindamycin, cefalexin, and amoxicillin-clavulanate are commonly used empirically. Treatment duration is typically three to four weeks minimum, or one week beyond clinical resolution.
Deep Pyoderma
When bacterial infection penetrates through the follicle wall and into the deeper dermis and subcutaneous tissue, the result is deep pyoderma. This is a far more serious condition, associated with significant pain, tissue destruction, and systemic signs including lethargy and fever in severe cases.
Deep folliculitis and furunculosis develop when inflamed, infected hair follicles rupture, releasing bacteria and keratin debris into the surrounding dermis. This provokes intense inflammation, and the skin develops nodules, draining tracts, haemorrhagic crusting, and ulceration. German Shepherd Dogs have a well-recognised predisposition to severe deep pyoderma that can become generalised across the back and hindquarters, often with an underlying immunological component.
Localised deep pyoderma can also develop at sites of pressure (pressure point pyoderma on elbows and hocks), muzzle and chin (acne in young dogs), and between the toes (interdigital furunculosis). Interdigital lesions in particular can be extremely painful and slow to resolve, particularly in short-coated breeds where stiff hairs can become embedded and act as a foreign body driving ongoing inflammation.
Deep pyoderma requires prolonged systemic antibiotic therapy — a minimum of six to eight weeks, and often longer. Culture and sensitivity testing is essential at this level of infection. Topical therapy with antiseptic soaks, shampoos, and whirlpool baths helps debride necrotic material and improve drug penetration. Surgical debridement may be necessary in severe or localised cases where tracts have developed.
The Importance of Finding the Underlying Cause
Every dog with recurrent or persistent pyoderma warrants a thorough diagnostic workup. In young dogs, demodicosis should be ruled out with skin scrapings. Allergy testing and dietary trials help identify atopic or food-allergic patients. Blood screening for hypothyroidism, hyperadrenocorticism, and other hormonal imbalances is appropriate in middle-aged to older dogs presenting with recurrent skin infections. Without addressing the predisposing factor, antibiotics will treat each episode but do nothing to prevent the next.
Antimicrobial stewardship is increasingly relevant in veterinary dermatology. Where possible, culture-directed therapy, minimum effective treatment duration, and maximal use of topical rather than systemic antibiotics help preserve the efficacy of antibiotics that both animals and people depend upon.