Fungi can infect the skin of a dog’s nose and the passages inside it. Fungi are living things such as moulds and yeasts. Several kinds can do this, including Cryptococcus, Blastomyces, Sporothrix and Aspergillus [1][2][3][4].
If your dog’s nose is swollen or badly ulcerated, or it has heavy discharge from the nose, take it to a vet now.
Why it is more serious than a skin infection
Some of these fungi do not stay in the skin. With cryptococcosis, the infection inside the nose can reach the brain and the eyes [1]. Blastomycosis is a body-wide fungal disease, and about half of affected dogs also get skin sores [2]. Mucocutaneous pyoderma, a bacterial infection at the edges of the lips and nostrils, is a different problem. For that infection, see mucocutaneous pyoderma in dogs.
Signs
Each fungus can show up a little differently:
- Cryptococcus: in about a quarter of dogs with this infection, open sores (ulcers) form on the nose, and sometimes on the tongue, gums, roof of the mouth or around the nails [1]. Cryptococcus can also cause long-lasting swelling and irritation inside the nose (chronic rhinitis), and in dogs it often damages the inner nose and forms a mass there [5].
- Blastomyces: lumps and raised patches that may break open. The flat skin at the tip of the nose (the nasal planum), the face and the nail folds are favourite spots [2].
- Sporothrix: sores with crusts can sit on a dog’s muzzle [3].
- Aspergillus: this mould grows inside the nose and sinuses. In one group of 30 dogs, every owner saw discharge from the nose, more than half saw nosebleeds and half saw sneezing. Some dogs lost the dark colour on the nose [4].
The nasal mucosa, the moist lining inside the nose, can be involved too, so heavy discharge is a warning sign [1][4].
How vets diagnose it
A vet may look at discharge or material from the nose or skin under a microscope (cytology). For cryptococcosis this finds the fungus in most cases, and a test for a part of the fungus (an antigen test) can both confirm the disease and track treatment [1]. A biopsy means taking a small piece of tissue to look at under a microscope [3].
When the fungus is inside the nose, vets often use a CT scan and look inside the nose with a small camera (rhinoscopy). These help find other problems in the nose at the same time, such as something stuck in it or a dental problem [4][5].
In the same group of dogs with Aspergillus, most did not get better on antibiotics alone, and some got worse [4].
For other causes of a sore or crusty nose, see dry, crusty nose in dogs.
Treatment
Your vet will advise on treatment for your dog. Some fungal nose infections need more than one round of treatment and repeated checks under anaesthesia, because signs at home do not always show whether the infection is gone [4].
At home, as directed by a vet:
- do not pick at the sores or crusts;
- do not put human or leftover products on your dog’s nose unless your vet says so;
- go back for every recheck your vet books.
When to see your vet
Take your dog to a vet now if its nose has:
- swelling [1];
- open or severe sores [1][2];
- heavy discharge, or bleeding [4].
The bottom line
Fungal infections of the nose can go deeper than the skin, and some can spread through the body. Swelling, open sores, nosebleeds or heavy discharge from the nose need a vet now, and only a vet can find the cause.
This article is for general information only and does not replace advice from your veterinarian. If your dog’s nose is swollen, badly ulcerated or running heavily, go to a vet now.
Sources
- Torres SMF. 4.5 Systemic Mycosis: Cryptococcosis, Small Animals. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/systemic-mycosis-cryptococcosis-small-and-large-animals/
- Torres SMF. 4.4 Systemic Mycosis: Blastomycosis, Small Animals. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/systemic-mycosis-blastomycosis-small-and-large-animals/
- Torres SMF. Subcutaneous Mycosis: Sporotrichosis, Small and Large Animals. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/subcutaneous-mycosis-sporotrichosis-small-and-large-animals/
- Rösch S, Oechtering GU. Primary and Secondary Sinonasal Aspergillosis in Dogs. Animals (Basel). 2025;15(19):2880. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC12524304/
- Cooley S, Galustanian G, Moon A, Summers S. CT findings of nasal cryptococcosis in cats and dogs: A case series. Vet Radiol Ultrasound. 2022;63(4):422-429. PMID 35279897. https://pubmed.ncbi.nlm.nih.gov/35279897/