Allergic Bronchitis in Dogs

Allergies are caused by the aggressive response of specialized immune cells to an allergen. When an allergen activates the immune system, it manufactures a protein that causes the immune cells to release histamine, a naturally occurring compound that has an inflammatory effect on the tissues it comes into contact with. When the histamine causes inflammation to the bronchial tubes, the swelling can make it difficult to breathe and causes wheezing and shortness of breath. It is also referred to as canine asthma and can be either chronic or acute.

Allergic bronchitis is the narrowing of the airways due to inflammation and swelling of the bronchi caused by exposure to an allergen. This disorder can be either chronic or acute.

Dogs tend to be more susceptible to an attack of allergic bronchitis after exertion. The wheezing that is the distinguishing symptom of this disorder is usually followed by a dry, hacking cough. Although mucus may be present in the bronchial tubes, the cough is non-productive. The continuing cough often causes the airways to constrict further, which restricts the amount of air entering the lungs, causing exhaustion and loss of appetite. If the lack of oxygen continues long enough, the gums will turn blue. When this occurs, the situation is life-threatening, and your pet needs emergency intervention.

Types 

Chronic allergic bronchitis is allergic bronchitis that lasts or reoccurs over several months. The most common environmental allergies, like pollens, molds, and dust, usually cause chronic allergic bronchitis. Several circumstances can trigger episodes of chronic allergic bronchitis such as obesity in the patient, long-term exposure to cold temperatures, and changes in  exertion levels. 

Acute allergic bronchitis is an allergic reaction that occurs either just once or over a period of just a few days or weeks. This may take place as a result of being triggered by an allergen that just isn’t encountered often, or it may be that a particular condition is triggering an allergic reaction that otherwise is too mild to detect like a bacterial or viral illness, or cross-reactive allergies.

When allergic bronchitis arises, the histamine that is released by the immune system, attacks the bronchial tubes, causing inflammation and swelling that can cause serious health concerns.There are several types of common environmental allergens that can trigger bronchitis. Common causes of allergic bronchitis can include:

• Cigarette smoke
• Pollen
• Mold
• Mildew
• Aerosol sprays 
• Dust mites
• Grain mites
• Dust

Bronchitis in canines can be caused by a number of disorders, including allergies. During the physical exam to diagnose your canine, special attention will be paid to the respiratory sounds and the color of your canine’s gums. In order to diagnose an ongoing cough, with or without attendant bronchitis, chest x-rays are often recommended to determine the condition of the lungs.

Blood and fecal tests may be run at this time as well. These tests can reveal a number of disorders with similar symptoms, such as kennel cough, fungal infections, or pneumonia. The blood work, as well as any analysis of other secretions, should show elevated levels of a particular type of cell called an eosinophil. Eosinophils are often elevated in response to fungal and parasitic diseases as well as during allergic reactions. A bronchoscopy may also be employed in order in order to look directly into the airway to check for parasites, foreign bodies, and tumors that may otherwise remain hidden.

The most effective treatment for allergic bronchitis is avoidance of the allergen. Because many allergens that cause bronchitis are airborne, it can be challenging to avoid the allergen so other methods may need to be employed. Your veterinarian may want to prescribe antihistamines to reduce the reactions to the histamine that has been released into the bloodstream. Antihistamines are not as effective in canines as they are in humans, however, and are successful in less than half the cases.

Bronchodilators and corticosteroids may also be used to allow the bronchial tubes to open by relaxing the muscles around the airway walls. Bronchodilators can be administered from a specially made canine inhaler, or as a pill, capsule, or syrup. Bronchodilators can lead to an increased heart rate, nervousness, or tremors in dogs and are not recommended for animals with high blood pressure or heart conditions. Antibiotics may also be recommended in the event that a concurrent bacterial infection also affects the patient.

Asthma inhalers may be recommended for dogs with allergic bronchitis that have attacks once a week or more. Inhalers for dogs are built on the same principle as human inhalers for similar disorders, but more closely resemble the asthma inhalers designed for small children. The asthma inhaler has a mask to place over the dog’s muzzle, which should be kept in place for at least 10 seconds per dose. The inhaler targets the respiratory system directly rather than having to be transported through the digestive system like pills or syrups will have to and are metered to help prevent cases of overdose.