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. Dogs with longer noses—such as retrievers, collies, and German shepherds—appear to develop the condition more often, though the reasons for this association are not fully understood. 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
Options & trade-offs
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