CONDITION

Aspergillosis (Nasal)

Nasal aspergillosis is a fungal infection of the nasal passages and sinuses, most often caused by a species of mould called Aspergillus fumigatus. The fungus can colonise the lining of the nose, leading to inflammation, discharge, and sometimes destruction of the delicate structures inside. It occurs most commonly in dogs, particularly those with longer noses, and is rare in cats. Owners often notice a persistent nasal discharge—sometimes clear, sometimes thick or containing blood—that may affect one or both nostrils. Sneezing, nosebleeds, or a change in the appearance of the nostril itself can also occur. The signs tend to develop gradually, and many dogs remain otherwise well in the early stages. This page explores what nasal aspergillosis may look like in practice, what is understood about how the infection takes hold, how it is investigated using imaging and sampling, and the range of approaches that exist for managing it. The goal is to help you understand what may be happening and what questions might be useful to consider.

Why this matters now

Nasal aspergillosis tends to affect young to middle-aged dogs, most commonly between two and seven years of age. Nasal aspergillosis is classically associated with dolichocephalic (long-nosed) breeds such as Collies, Greyhounds, and Dachshunds. German Shepherd Dogs and retrievers are also over-represented in some case series, but this is not explained by nose length; proposed explanations include environmental spore exposure and, in German Shepherds specifically, a tendency toward local immune dysfunction such as relative IgA deficiency, rather than nasal anatomy. There is no clear seasonal pattern, and exposure to mould spores is widespread in the environment, so why certain individuals develop infection whilst others do not remains unclear.

The condition often develops gradually over weeks or months, with signs that may initially be intermittent or mild. In some cases, the discharge or sneezing becomes persistent and more obvious over time, whilst in others the pattern can remain relatively stable for extended periods. The course varies between individuals, and some dogs may show little progression, whilst others develop more widespread changes within the nasal passages. Without intervention, the infection typically does not resolve on its own.

Signals & patterns

Early signals

Persistent nasal discharge

A discharge from one or both nostrils that continues for more than a week or two, often clear or mucoid at first. The discharge may increase in volume or change in character over time, and tends not to respond to rest or supportive care.

Increased sneezing

Episodes of sneezing that occur more frequently than usual, sometimes in bouts. The sneezing may seem to be triggered by irritation within the nose itself, rather than by obvious external factors.

Pawing at the face

A dog may rub or paw at the muzzle or nose, suggesting discomfort or irritation in the nasal passages. This behaviour may be subtle and intermittent, and can be easy to overlook in the early stages.

Occasional blood-tinged discharge

Small amounts of blood may appear in the nasal discharge, either as streaks or as a slight pink tinge. This can occur sporadically, and may not be present every day.

Later signals

Nosebleeds

Fresh blood dripping from one or both nostrils, which may occur spontaneously or after sneezing. The bleeding can range from small spots to more obvious flows, and may alarm owners when it first appears.

Changes in nostril appearance

The nostril itself may lose its normal smooth, moist appearance, and can become depigmented, ulcerated, or distorted in shape. These changes reflect more advanced involvement of the tissues at the opening of the nasal cavity.

Noisy or obstructed breathing

Breathing through the nose may become audible, with snorting or snuffling sounds, particularly during rest or sleep. In some cases, the dog may begin to breathe more through the mouth if airflow through the nose is significantly reduced.

Click to read about the biological mechanisms

How this is usually investigated

Investigation of nasal aspergillosis typically begins with a review of the pattern and duration of signs, followed by examination of the nose and assessment of the nasal airways. As the picture develops, imaging and sampling are often used to visualise the extent of changes within the nasal passages and to identify the presence of fungal organisms. The combination of findings from different tests helps to build a clearer understanding of what may be present.

Physical examination and rhinoscopy

Purpose: Direct inspection of the nasal passages, sometimes using a small camera (rhinoscope), can reveal visible fungal plaques, areas of tissue destruction, or changes to the turbinate bones. It also allows samples to be collected from affected areas.
Considerations: Rhinoscopy requires sedation or anaesthesia and provides a view only of accessible portions of the nasal cavity. Some changes may lie deeper within the sinuses, beyond the reach of the camera, and the procedure itself carries small risks associated with anaesthesia.

Computed tomography (CT)

Purpose: CT imaging produces detailed cross-sectional pictures of the nasal chambers and sinuses, showing the extent of turbinate destruction, soft tissue changes, and involvement of surrounding bone. It can reveal patterns that are characteristic of fungal infection.
Considerations: CT requires general anaesthesia and access to specialist imaging equipment, which may involve referral. It provides structural detail but cannot confirm the presence of fungal organisms on its own, so findings are typically interpreted alongside other tests.

Fungal culture and cytology

Purpose: Samples collected from nasal discharge or tissue can be examined under a microscope (cytology) to look for fungal elements, or grown in the laboratory (culture) to identify the specific organism involved. Positive results support the diagnosis.
Considerations: Aspergillus spores are present in the environment, so samples can occasionally be contaminated, leading to false positive results. Conversely, culture may fail to grow the fungus even when infection is present, particularly if samples are taken from areas with little active fungal growth.

Serology (blood testing for fungal antibodies)

Purpose: Blood tests can detect antibodies against Aspergillus species, indicating that the immune system has encountered the fungus. Results are sometimes used to support other findings.
Considerations: Serology can produce false negatives in early infection or in dogs with localised disease, and false positives can occur if a dog has been exposed to the fungus without developing infection. It is generally interpreted alongside imaging and sampling rather than in isolation.

Radiography (X-rays)

Purpose: Plain radiographs of the skull can sometimes reveal increased opacity in the nasal passages or loss of the normal turbinate pattern, suggesting chronic inflammation or tissue destruction.
Considerations: Radiography is less detailed than CT and may miss subtle changes, particularly in the early stages. It can provide useful preliminary information but is often followed by more advanced imaging if nasal aspergillosis is suspected.

Options & trade-offs

Management of nasal aspergillosis typically involves approaches that aim to reduce the fungal burden within the nasal passages, sometimes combined with measures to support healing and reduce inflammation. Treatment is usually individualised, taking into account the extent of disease, the practicalities of different methods, and what is workable for a particular dog and household. Different combinations suit different circumstances, and the response can vary between individuals.

Topical antifungal infusion

A concentrated antifungal solution (commonly clotrimazole or enilconazole) is infused directly into the nasal passages whilst the dog is under general anaesthesia, with the aim of delivering a high dose of medication to the site of infection. The solution is typically left in contact with the nasal lining for a defined period, often around one hour, before being drained. Some protocols involve a single infusion, whilst others use two sessions separated by a short interval.

Trade-offs: This approach requires general anaesthesia and specialist equipment to ensure the solution reaches all affected areas and does not enter the airways or sinuses inappropriately. Response rates vary, and some dogs may require repeat treatment. It does not address underlying factors that may have allowed the infection to establish, and recurrence can occur.

Systemic antifungal medication

Oral antifungal drugs, such as itraconazole or posaconazole, are given over an extended period—often several months—with the aim of reducing fungal load throughout the nasal passages. The medication is absorbed into the bloodstream and distributed to infected tissues, where it inhibits fungal growth.

Trade-offs: Treatment is prolonged and requires regular administration at home, which may be challenging for some owners. The drugs can have side effects, including liver enzyme changes and gastrointestinal upset, so periodic blood monitoring is often suggested. Response can be slower than with topical infusion, and success is variable.

Surgical debridement

In some cases, surgical removal of visible fungal plaques and damaged tissue can be performed via rhinoscopy or open surgery. The procedure aims to reduce the physical burden of infection and improve access for topical antifungal treatment, which is often given at the same time.

Trade-offs: Debridement alone typically does not eliminate the infection, so it is usually combined with other treatments. Surgery carries risks associated with anaesthesia and potential bleeding from the inflamed nasal lining. It may be considered when there is extensive fungal material or obstruction, but outcomes depend on the thoroughness of removal and the response to accompanying antifungal therapy.

Combination approaches

Some protocols combine topical infusion with a period of systemic antifungal medication, or use surgical debridement followed by topical treatment, with the aim of addressing the infection through multiple routes. The choice of combination depends on the extent of disease, the facilities available, and the individual dog's response to initial treatment.

Trade-offs: Combination approaches can involve greater cost, longer treatment duration, and cumulative risks from anaesthesia and medication. They may offer improved outcomes in some cases, but the benefit varies, and there is no single combination that suits all individuals. Close monitoring is often needed to balance effectiveness and tolerability.

Common misconceptions

Misconception:

"Nasal aspergillosis is caused by a weak immune system or underlying illness."

Reality:

Most dogs with nasal aspergillosis are otherwise healthy, with no detectable defect in their immune system. The fungus is widespread in the environment, and the reasons why it colonises the nasal passages in some individuals and not others remain unclear. Local factors, such as minor trauma or the anatomy of the nasal chambers, may play a role, but generalised immune compromise is not typically present.

Misconception:

"Once treated, nasal aspergillosis will never come back."

Reality:

Recurrence can occur even after apparently successful treatment, particularly if fungal organisms remain in small pockets within the nasal passages or sinuses that were not fully reached by medication. The risk of recurrence varies depending on the treatment used, the completeness of the response, and individual factors. Some dogs remain clear for years, whilst others may develop signs again and require further intervention.

Misconception:

"Antibiotics will clear up a fungal nasal infection."

Reality:

Antibiotics target bacteria, not fungi, and do not have any direct effect on Aspergillus organisms. Nasal discharge from aspergillosis can sometimes become secondarily infected with bacteria, in which case antibiotics may reduce certain signs temporarily, but they do not address the underlying fungal infection. Specific antifungal treatment is needed to reduce the fungal burden.

Related conditions

Cryptococcosis

Cryptococcosis is another fungal infection that can affect the nasal passages and sinuses, particularly in cats, and shares several clinical features with nasal aspergillosis—including nasal discharge, sneezing, and visible changes to the nostril. The two conditions can present similarly on initial examination, though they tend to affect different species and may require different diagnostic approaches to distinguish them.

Chronic Upper Respiratory Disease in Cats

Chronic upper respiratory disease in cats can sometimes be confused with nasal aspergillosis when nasal discharge and sneezing persist over time, though the underlying causes differ. Both conditions involve prolonged inflammation of the nasal passages, and imaging or sampling may be needed to differentiate a fungal infection from the viral or bacterial triggers more common in cats.

Syringomyelia (CM/SM)

Nasopharyngeal polyps can cause similar signs to nasal aspergillosis—persistent nasal discharge, noisy breathing, and changes in airflow—because both conditions occupy and obstruct the nasal passages or the space behind them. The distinction often rests on imaging and examination under anaesthesia, as polyps are benign growths rather than infectious lesions.

Squamous Cell Carcinoma of the Nasal Planum

Squamous cell carcinoma of the nasal planum can occasionally extend into the nasal passages, and the resulting tissue destruction, discharge, or changes in nostril appearance may overlap with signs seen in nasal aspergillosis. Both conditions can alter the structure of the nose over time, and biopsy or advanced imaging is often needed to confirm which process is present.

Dermatophytosis (Ringworm)

Dermatophytosis is another fungal infection, though it typically affects the skin, hair, and claws rather than the nasal passages. While the fungi involved and the tissues affected differ, both conditions illustrate how environmental moulds and fungi can establish themselves in an animal's body, and both may require culture or sampling to confirm the organism responsible.

Understanding how nasal aspergillosis relates to the broader workings of the immune system and inflammatory responses can provide useful context for the patterns you observe. The pillar on Immune & Inflammatory Health explores these connections in more depth. If the signs have been present for some time, or if you are weighing different management approaches, the shape and timing of investigation and treatment may be a useful conversation to have at the next appointment.