Pyoderma is a bacterial skin infection. Mucocutaneous pyoderma is a form that settles where haired skin meets the moist lining of the body, most often the lips and the skin around the mouth [1]. It can also show up on the eyelids, around the nose, and around the anus and genitals [1]. Perioral means around the mouth, and periocular means around the eyes.
Have your vet check any crusts or sores on your dog’s lips or nose. Another disease can look the same.
For pyoderma in general, see pyoderma in dogs.
Where it shows
Mucocutaneous means the edge where haired skin meets the moist lining of the mouth or nose. A report of three German shepherd dogs notes that the lips, the nasal planum, the nostrils and the skin around the mouth are the usual places, with the eyelids, vulva, prepuce and anus affected less often [4]. The nasal planum is the hairless tip of the nose, and the nares are the nostrils.
Signs
International guidelines on canine pyoderma describe redness, swelling, crusts, ooze, shallow sores (erosions), deeper sores (ulcers) and changes in skin color at these junctions, sometimes with hair loss around the edges [1]. Erosions are shallow sores, and ulcers are deeper ones.
The same guidelines group it with the superficial pyodermas. Its sores can look like a lip-fold infection, only worse, and sometimes go deep enough to ulcerate [1].
What causes it
The germs behind it are not well documented. The guidelines say they are likely bacteria that normally live on the skin, with Pseudomonas, another type of bacteria, possible in moist spots [1]. Any breed can get it, but German shepherd dogs are reported to be more prone [1].
The lupus look-alike
Discoid lupus and a related form called mucocutaneous lupus are autoimmune diseases, not infections, yet they can look much like mucocutaneous pyoderma [1][2]. A study of nose biopsies found that the two diseases share many features both on the dog and under the microscope, which makes them hard to tell apart [3]. Only a vet can tell them apart.
A biopsy means taking a small piece of skin to look at under a microscope. In that study, scoring the biopsies alone could not predict which disease a dog had; the answer came from how each dog responded to treatment [3]. German shepherd dogs and their crosses made up a large share of the cases [3]. The guidelines advise a biopsy if sores remain after the infection has been treated well [1].
For lupus and other causes of a crusty nose, see dry, crusty nose in dogs.
How vets diagnose it
The diagnosis rests on where the sores are and on cytology, a look at a sample of the ooze or crust under a microscope [1]. Finding infection-fighting white blood cells (neutrophils) and bacteria supports infection [1]. The diagnosis is confirmed when the sores clear up with treatment for the infection [1].
Treatment
Your vet will advise on treatment for your dog.
At home, as directed by a vet:
- do not pick at the crusts;
- do not put human or leftover products on your dog’s lips or nose unless your vet says so;
- go back for every recheck your vet books.
When to see your vet
See your vet if your dog has:
- crusts or ooze at the edges of the lips or nostrils [1];
- shallow or deeper sores (erosions or ulcers) where the lips or nose meet the skin [1];
- redness, swelling or color change on the lips, eyelids or nose [1].
The bottom line
Mucocutaneous pyoderma is a bacterial infection at the edges of a dog’s lips and nostrils. Lupus can look the same, and only a vet can tell them apart.
This article is for general information only and does not replace advice from your veterinarian. If your dog has crusts or sores on its lips or nose, see your vet.
Sources
- Loeffler A, Cain CL, Ferrer L, Nishifuji K, Varjonen K, Papich MG, et al. Antimicrobial use guidelines for canine pyoderma by the International Society for Companion Animal Infectious Diseases (ISCAID). Vet Dermatol. 2025;36(3):234-282. Open access, CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC12058580/
- Torres SMF. 2.7 Facial Discoid Lupus Erythematosus, Dogs and Cats. Small and Large Animal Dermatology Handbook, Vol. 2. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology2/chapter/facial-discoid-lupus-erythematosus-dogs-and-cats/
- Wiemelt SP, Goldschmidt MH, Greek JS, Jeffers JG, Wiemelt AP, Mauldin EA. A retrospective study comparing the histopathological features and response to treatment in two canine nasal dermatoses, DLE and MCP. Vet Dermatol. 2004;15(6):341-8. PMID 15585008. https://pubmed.ncbi.nlm.nih.gov/15585008/
- Bassett RJ, Burton GG, Robson DC. Antibiotic responsive ulcerative dermatoses in German Shepherd Dogs with mucocutaneous pyoderma. Aust Vet J. 2004;82(8):485-9. PMID 15359964. https://pubmed.ncbi.nlm.nih.gov/15359964/