Most cases of asthma in dogs are often viewed as an allergenic condition. Thus, there are periods of flare-ups and situations that are worse than others; a dog can also go without symptoms for months before he suffers from another bout of asthma attack.
Since asthma is commonly triggered by potential allergens in the dog’s environment, taking steps to identify these external triggers can help you prevent or reduce your pet’s exposure, as well as manage asthma attacks.
One important trigger of asthma attacks in dogs is dust mites. Dust mites are microscopic organisms that are almost always present to some degree even in houses that are regularly cleaned. In addition to regular cleaning and proper disposal of dirt and dust, the use of air filter, anti-static dusters and cloth wipes can help keep the level of dust mites to a minimum.
Source: Common Triggers Of Canine Asthma