Little red bumps on the belly. Round, crusty rings on the back. A patchy, “moth-eaten” coat. If your vet has said the word pyoderma, you are dealing with one of the most common reasons dogs visit the clinic, and one of the most common reasons they are prescribed antimicrobials. [1]
This guide explains what pyoderma is, why it happens, what your vet is likely to do, and how you can help stop it from coming back.
What is pyoderma?
The word pyoderma means “pus in the skin.” [2] It is the medical name for a bacterial skin infection.
In dogs, the main bacterium involved is Staphylococcus pseudintermedius. The 2025 guidelines from the International Society for Companion Animal Infectious Diseases (ISCAID) report that this species is found in more than 90% of canine pyoderma cases. [1] It is not a germ that “invades” from outside. It normally lives on healthy dogs, and studies show the bacteria found in infected skin are genetically the same as those carried on the dog’s own body. [1]
That leads to the most important idea in this whole article.
Pyoderma is almost always a symptom
ISCAID states plainly that bacterial skin infection always occurs secondary to a primary underlying cause. [1] The bacteria were already there. Something weakened the skin’s defenses and let them take over.
Common underlying causes include:
- Allergies, including environmental allergies (atopic dermatitis) and food allergies [1][2]
- Fleas and other parasites [1][2]
- Hormonal diseases such as hypothyroidism and Cushing’s disease [2]
- Skin folds and friction, for example in bulldogs, Shar Peis and overweight dogs [1]
- Poor grooming and matted coats [2]
ISCAID notes that when recurrent pyoderma starts in a young dog (under about 3 years), allergic skin disease is one of the most likely causes. In older dogs, vets may look harder for hormonal problems or other illness. [1]
If only the infection is treated and the cause is not, pyoderma tends to come back.
The three depths of pyoderma
Vets classify pyoderma by how deep in the skin the infection goes, because depth decides the treatment. [1]
1. Surface pyoderma
Bacteria are confined to the very top layer of skin. Examples include: [1]
- Hot spots (acute moist dermatitis): red, oozing, fast-growing sores. See our guide to hot spots on dogs.
- Skin fold dermatitis (intertrigo): redness, odor and discharge in lip, face, tail or vulvar folds.
2. Superficial pyoderma
Infection of the outer skin and the hair follicles. This is the most common type. [1]
The classic form, superficial bacterial folliculitis, shows up as: [1]
- Small red bumps (papules) and pimples (pustules)
- Epidermal collarettes: round, scaly rings
- Patchy hair loss; in short-coated breeds the coat can look “moth-eaten”
- Itch, often
- Typical sites: belly, inner thighs and back of the neck
3. Deep pyoderma
Infection goes into the deeper layers of skin and sometimes below. [1] Signs can include: [1][2]
- Painful, swollen areas
- Bloody crusts, draining tracts and ulcers
- Pus and bad odor
- Swollen lymph nodes
- A dog that seems unwell
Deep pyoderma is more serious and always needs a vet.
How vets diagnose pyoderma
Looking at the skin
Your vet will check the whole body, not just the spot you noticed. Hair may be trimmed to see lesions clearly. [1]
Cytology
This is a quick, inexpensive test. Your vet presses tape or a slide to the skin and looks under the microscope for bacteria and inflammatory cells. ISCAID recommends cytology in every suspected pyoderma case before antimicrobials are given. [1]
Culture and sensitivity testing
A sample is sent to a lab to grow the bacteria and see which drugs work against them. ISCAID strongly recommends this for deep pyoderma and whenever resistance is a concern, for example: [1]
- Repeated pyoderma
- More than one course of oral antibiotics in the past 6 months
- A previous resistant infection in the dog or the household
- No improvement after 5 to 7 days of oral antibiotics
- New lesions appearing during treatment
Tests for the underlying cause
Depending on your dog, this may mean flea control trials, skin scrapes for mites, allergy workups, food trials, or blood and urine tests for hormonal disease. [1][2]
How pyoderma is treated
Your vet will choose treatment for your individual dog. Current guidance has shifted in recent years, so it is worth knowing what the experts now recommend.
Topical treatment comes first
For surface and superficial pyoderma, ISCAID says topical antimicrobial therapy alone is the treatment of choice. [1] That means medicated shampoos, sprays, mousses, wipes, creams or gels your vet recommends.
- For superficial folliculitis, topical therapy alone worked in 12 of 13 published clinical trials reviewed by ISCAID. [1]
- Ingredients with clinical evidence include 2 to 4% chlorhexidine and 2.5% benzoyl peroxide. [1]
- In one randomized trial, a chlorhexidine shampoo and solution worked as well as an oral antibiotic after 4 weeks. [1]
Using topical products well matters. Follow your vet’s instructions on contact time, frequency and how long to continue.
Oral antibiotics when needed
ISCAID reserves oral (systemic) antibiotics for: [1]
- Deep pyoderma, where they are always needed and should be chosen based on culture results
- Superficial pyoderma that does not respond to topical treatment
When oral antibiotics are used, ISCAID suggests an initial course of about 2 weeks for superficial and 3 weeks for deep pyoderma, followed by a recheck to decide whether to continue. [1] Your vet may set a different plan for your dog. Always give the full course as prescribed and never use leftover antibiotics.
Why vets are careful with antibiotics
Repeated courses of antibiotics are a main risk factor for methicillin-resistant Staphylococcus pseudintermedius (MRSP), a strain resistant to many common antibiotics. [1] Resistant infections look the same as ordinary ones, which is why culture testing matters. [1] The good news is that ISCAID reports topical antiseptics have stayed effective against these resistant staphylococci and that the outlook for resistant pyoderma is considered good. [1] Because resistant bacteria can spread between animals and to people, your vet may suggest extra hygiene steps at home. [1]
Treating the itch and the cause
Itchy dogs damage their skin further. Your vet may treat the itch and inflammation, and will work on the underlying cause. For dogs whose pyoderma keeps coming back because of allergies, ISCAID says controlling the allergy should be prioritized over repeated antibiotics. [1]
A note on bleach and hypochlorous acid
You may see home remedies online suggesting diluted bleach baths. ISCAID warns that household bleach at the strengths sold for cleaning (about 1.5 to 8%) is not safe for skin, and that diluting it enough to be safe for dogs (under 0.05%) creates a real risk of mixing errors that could harm the dog or the owner. [1] Do not try this at home.
Hypochlorous acid is a different, related chlorine compound. ISCAID describes it as a natural antimicrobial that mammals’ own white blood cells make, notes it has been shown to be safe as an ear flush in dogs at 0.015%, and describes it as safe for use in open wounds. [1] That does not mean every product is suitable for every skin problem. Ask your vet before using any product on infected skin, and do not use it in place of a vet visit.
Can pyoderma be prevented?
You cannot prevent every infection, but these steps help:
- Year-round parasite control suited to your area. ISCAID says it should be in place before antibiotics are even considered. [1]
- Manage allergies with your vet, not just the infections they cause. [1]
- Ask about maintenance topical therapy. ISCAID notes that regular, proactive use of antiseptic products may help prevent recurrences. [1]
- Keep skin folds clean and dry, and help overweight dogs lose weight to reduce friction. [1]
- Groom regularly to avoid mats that trap moisture. [2]
- Recheck visits. If your dog needs oral antibiotics more than once a year for skin infections, ISCAID says the search for the underlying cause should be repeated or stepped up. [1]
When to see your vet
Book a visit if you notice:
- Red bumps, pimples, crusty rings or patchy hair loss
- Itching, licking or chewing that does not settle
- A skin problem that keeps coming back
Go promptly if there is pain, swelling, bleeding, draining sores, a bad smell, fever, lethargy or loss of appetite. These can point to deep pyoderma.
Frequently asked questions
Is pyoderma contagious to people or other dogs?
The usual bacterium, S. pseudintermedius, normally lives on dogs, and infection happens because of a problem in that dog’s skin. [1] Resistant strains, however, can spread between animals, to people and into the environment, so your vet may advise hygiene measures, especially if your dog has a resistant infection. [1] Wash your hands after applying treatments.
What does pyoderma look like on a dog?
Superficial pyoderma usually shows as small red bumps, pimples, round scaly rings (collarettes) and patchy hair loss, often on the belly, inner thighs or neck. [1] Deep pyoderma looks more severe: painful swelling, bloody crusts and draining sores. [1]
Can pyoderma go away on its own?
It may improve briefly, but because pyoderma is driven by an underlying cause such as allergies or fleas [1], it often returns or worsens without proper treatment. See your vet.
Does my dog need antibiotic pills?
Not always. Current ISCAID guidelines recommend topical treatment alone for most surface and superficial pyoderma, and reserve oral antibiotics for deep infections or cases that do not respond. [1]
How long does treatment take?
It depends on the depth. Surface and superficial cases often respond within a few weeks. Deep pyoderma usually takes longer. Treatment generally continues until every lesion has cleared, and your vet will recheck your dog before it stops. [1][2]
Why does my dog’s pyoderma keep coming back?
Usually because the underlying cause, most often allergies, parasites or hormonal disease, is not yet controlled. [1][2] ISCAID advises that if a dog needs oral antibiotics more than once a year, the search for the cause should be intensified. [1]
Can I use human acne products or creams?
Do not use human products on your dog without your vet’s advice. Some ingredients and strengths are not suitable for dogs, and dogs often lick treated areas.
The bottom line
Pyoderma is a bacterial skin infection, usually caused by bacteria that already live on your dog, taking advantage of skin weakened by allergies, parasites, hormonal disease or friction. Treatment today leans on topical products first and careful, culture-guided antibiotics when needed. Long-term success depends on finding and managing the underlying cause.
See your vet for any new rash, bumps or crusts, and promptly if your dog is painful or unwell.
Related guides: why is my dog so itchy, seasonal allergies in dogs, dog dandruff and dry, flaky skin, hair loss in dogs, dog eye discharge and red eyes, cat ear problems, dog scooting and anal gland problems, lick granuloma in dogs, cat chin acne, eosinophilic granuloma complex in cats, ticks on dogs and cats, hives and facial swelling in dogs, dry, crusty nose in dogs, elbow hygroma in dogs, dark skin patches on dogs, lice on dogs and cats, maggots and warbles in dogs and cats, sarcoptic mange (scabies) in dogs, pemphigus foliaceus in dogs and cats, porcupine quills in dogs, mange in cats, lumps and bumps on cats, pyoderma in cats, warts on dogs and cats, skin worms in dogs and cats, cowpox in cats, fly and mosquito bites, hair loss in cats, nail and nail-bed problems, footpad problems in cats, dermatomyositis in Collies and Shelties, sebaceous adenitis in dogs, skin lymphoma in dogs and cats, photosensitization in dogs and cats, skin melanoma in dogs and cats, soft tissue sarcoma in dogs, fragile, stretchy skin (cutaneous asthenia), skin hemangioma and hemangiosarcoma, eosinophilic skin lesions in dogs, superficial necrolytic dermatitis in dogs, yeast infection on dog skin, nodular dermatofibrosis in German Shepherds, color dilution alopecia in dogs, alopecia X in dogs, ichthyosis in dogs, dermoid sinus in dogs, skin cysts in dogs, footpad hyperkeratosis in dogs, puppy strangles, sporotrichosis in cats, lethal acrodermatitis in Bull Terriers, frostbite in dogs and cats, skin signs of internal cancer in cats, ear-tip sores in dogs, aural hematoma in dogs and cats, solar dermatitis in cats, auricular chondritis in dogs and cats, contact dermatitis in dogs and cats, proliferative and necrotizing otitis externa in cats, ear flap hair loss in dogs, vitiligo in dogs and cats, feline atopic skin syndrome, hair follicle and basal cell tumors, flea allergy dermatitis, histiocytoma in dogs, dermatophilosis, sebaceous gland tumors, mast cell tumors, hereditary hair loss, lipomas in dogs, interdigital furunculosis in dogs, ceruminous gland tumors, demodectic mange in dogs, perianal gland tumors in dogs, squamous cell carcinoma of the skin, cutaneous plasmacytoma in dogs, sweat gland tumors in dogs and cats, chiggers in dogs and cats, injection-site sarcoma in cats, food allergy skin signs in dogs and cats, pressure sores in dogs and cats, degloving injuries in dogs and cats, slow-healing wounds in dogs and cats, lentigo in orange cats, epidermolysis bullosa in dogs and cats, electrical cord burns in dogs and cats, cutaneous histiocytosis in dogs, cutaneous mucinosis in Shar-Pei dogs, nerve sheath tumors of the skin, how vets diagnose skin problems, skin tags and fibromas, how dog and cat skin works, malignant fibrous histiocytoma in cats, wart-like skin growths in dogs, hives in cats, epitheliogenesis imperfecta, sex hormone skin problems in dogs, familial vasculopathy in puppies, skin signs of nerve disorders in dogs, albinism and white coats, ear margin seborrhea in dogs, how vets use shampoos and topical care, how wounds heal in dogs and cats, stitched or left open wounds, bandages on dogs and cats, gunshot injuries in dogs and cats, psoriasiform-lichenoid dermatosis in Springer Spaniels, bite wounds in dogs and cats, nasal hyperkeratosis in dogs, arteritis of the nasal philtrum, mucocutaneous pyoderma in dogs, fungal nose infections in dogs, calcinosis cutis in dogs, cancer that spreads to the skin, acquired aurotrichia, exfoliative cutaneous lupus, impetigo in dogs, urticaria pigmentosa in cats, post-grooming furunculosis in dogs, skin signs of hypothyroidism in dogs, skin signs of Cushing’s disease in dogs, skin signs of leishmaniosis in dogs, nocardiosis in cats, actinomycosis in dogs, cryptococcosis in cats, valley fever in cats, protothecosis in cats, nocardiosis in dogs, leishmaniosis in cats, pythiosis in dogs, brown recluse spider bites, blastomycosis in dogs, wound drains in dogs and cats, skin flaps and grafts, snakebites on dogs and cats, systemic histiocytosis, perianal fistula in dogs, tetanus in dogs and cats, lipomas in cats, skin cysts in cats, phaeohyphomycosis, fungal mycetomas, lagenidiosis in dogs, flea and tick product reactions, prescription skin creams for people, hormone gels and hair loss in pets, ear infections in dogs, dog paw problems, lumps and bumps on dogs, ringworm in dogs and cats and minor wound care for dogs and cats.
This article is for general information only and is not a substitute for professional veterinary advice, diagnosis or treatment. Always consult your veterinarian about your pet’s health. If you think your pet has a medical emergency, contact your veterinarian or an emergency animal hospital right away.
Sources
- Loeffler A, Cain CL, Ferrer L, et al. Antimicrobial use guidelines for canine pyoderma by the International Society for Companion Animal Infectious Diseases (ISCAID). Veterinary Dermatology. 2025. doi:10.1111/vde.13342. https://pmc.ncbi.nlm.nih.gov/articles/PMC12058580/
- Torres SMF. Canine Pyodermas. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025 (CC BY 4.0). https://open.lib.umn.edu/animaldermatology/chapter/canine-pyodermas/