Allergic Bronchitis in Dogs

What is allergic bronchitis?

Allergic bronchitis is an overreaction or hypersensitivity of the airways to inhaled allergens like dust, pollen, smoke, mold, and aerosolized particles like air fresheners. Parasites (heartworm) and fungal infections can cause similar signs. Rarely, eating certain proteins may also trigger allergic bronchitis.

What is the difference between allergic bronchitis and chronic bronchitis?

Allergic bronchitis is triggered by a specific allergen or group of allergens and appears suddenly. It may recur seasonally. 

Chronic bronchitis is caused by the effects of chronic airway inflammation, which causes irreversible changes to the airways. It generally causes more persistent signs that last a month or more and don’t improve without treatment. 

Allergic bronchitis can contribute to chronic bronchitis if the inflammation is not controlled adequately.

What part of the respiratory system is involved in allergic bronchitis?

In general terms, the respiratory system is divided into two parts. The upper respiratory tract consists of the nose, nasal sinuses, throat, and trachea (windpipe), while the lower respiratory tract consists of the small airways (bronchi and bronchioles) and the alveoli (the small air sacs deep in the lung tissue where oxygen exchange occurs). Allergic bronchitis is a condition of the lower respiratory tract.

How does allergic bronchitis affect the lungs?

The pet’s overreaction to the allergen causes swelling of the lining of the airways, thickening of the muscles around the airways, overproduction of mucus, and tightening of the airways. All these reactions reduce your dog’s ability to breathe comfortably.

What dogs are commonly affected?

Affected dogs are usually younger to middle-aged.

What are the signs of allergic bronchitis?

Signs of allergic bronchitis include:

• A harsh, dry cough that occurs suddenly
• A cough that is worsened or triggered by exercise or irritation of the trachea (windpipe), such as by pulling on a collar
• A cough that recurs at certain times of year when allergens are plentiful (e.g., pollen)
• Wheezing or trouble breathing (rare)

What other conditions are like allergic bronchitis?

Allergic bronchitis has signs similar to other diseases, including:

• Fungal, bacterial or parasitic infections
• Heartworm disease
• Cancer
• Collapsing trachea

How is allergic bronchitis diagnosed?

Your veterinarian may suspect allergic bronchitis based on their physical exam findings and the sudden onset of a dry cough. If they note a recurrence of similar signs following certain exposures (e.g., times of the year known to have higher pollen counts), it may add to this suspicion. Your vet may recommend several tests to rule out other causes and confirm this diagnosis:

• Complete blood count (CBC) and biochemistry profile to assess general health.
• Specific blood or fecal tests to rule out parasitic diseases like heartworm or lungworm.
• Chest radiographs (X-rays) may show changes that reflect the airway inflammation but not what caused it.
• Bronchoscopy allows a direct view of the inside of the airways and may be used to perform of a bronchoalveolar lavage (BAL), which allows collection of fluid, mucus, and cells from the airway that can confirm or rule out infection or inflammation.
• Allergy testing may be recommended on your dog’s blood or skin if your dog also has signs of skin allergy (atopy).

What is the treatment for allergic bronchitis?

Treatment for allergic bronchitis involves reducing allergen exposure and administering medications that open the airways and reduce inflammation.

• Avoid smoking or using air freshener sprays around your dog. Using air purifiers may further reduce allergen exposure.
• Corticosteroids like prednisone are used to reduce inflammation and may be given orally or with an inhaler. Oral medication works more quickly, so may be used on initial diagnosis as your dog starts inhaler therapy. Inhaled corticosteroids (fluticasone or Flovent®) are preferred, as there is less effect on the rest of the body and fewer side effects.
• In severe cases, bronchodilators (medications that open the airway) may be recommended, like theophylline or aminophylline.
• If allergic bronchitis is suspected to be part of a more widespread allergic disease like atopy, allergen-specific immunotherapy may be recommended, based on allergy testing.
• Nebulization (having your dog breathe moisturized air) may be recommended to dilute thick mucus, allowing your dog to clear it with less effort.
• Cough suppressants like hydrocodone or butorphanol may make your dog more comfortable but need to be used as your veterinarian recommends. Cough suppressants may reduce clearance of the mucus buildup.

What is the prognosis?

Allergic bronchitis cannot be cured; long-term or recurrent therapy may be needed. Your veterinarian may recommend routine recheck examinations and radiographs. Medication frequency may be adjusted depending on how your dog is doing. Generally, giving steroid medications at the lowest dose and frequency that manages your dog’s signs is recommended.

Your dog may also experience flares of coughing when the offending allergen is higher than usual, necessitating follow-up and often a temporary increase in your dog’s medications. Other diseases can also cause recurrence of the cough, so your veterinarian may recommend additional diagnostics to ensure your dog is getting targeted care.