Dogs have sensitive airways that should expand and contract in order to let the right amount of oxygen into the lungs. If there is a problem with the airways, it can cause wheezing as they are not expanding enough and the oxygen must squeeze its way through the tight airways. Failure of expansion in the airways can occur if your dog has:
Asthma
Dogs, like humans, can develop asthma when the large upper airways undergo spasms and constrictions. Asthma in dogs, which is also known as allergic bronchitis, is often caused by something in the environment that is causing a reaction. Some of these allergens include cigarette smoke, dust or smoke from fireplaces and wood-burning stoves, and aromas from air fresheners and deodorizers. Your dog can be more susceptible to allergic bronchitis if he is young or middle-aged, although older dogs are not immune. It is also more common in older smaller dog breeds. Asthma, or allergic bronchitis, can often be treated with medication but can become chronic and very severe if overlooked and left for too long. Symptoms aside from wheezing can include a dry hacking cough and respiratory distress.
Allergies
Allergies to pollen, dust or cigarette smoke can also cause wheezing. Some dogs can also develop allergies to certain insect stings or bites. Wheezing might be accompanied by itching of the skin, sneezing and/or coughing. In some cases, there may be runny discharge from the eyes or nose, and sometimes vomiting or diarrhea.
Allergies in dogs can be fairly common in all breeds, and will usually appear between the age of six months to two years old.
Kennel Cough
Kennel cough is a respiratory disease that can be highly contagious. It is usually acquired in places where a large amount of canines congregate, such as doggie daycare, dog parks, shows or training groups, as well as kennels (hence the name). The most obvious symptom is a strong cough, which will be accompanied by wheezing, sneezing, a
loss of appetite, lethargy and sometimes a low fever. Mild kennel cough can be treated with a few weeks of rest, but your vet may choose to prescribe cough medication to ease the symptoms or antibiotics to prevent secondary infection. If your dog is often in contact with other canines, it may be wise to get a vaccination to prevent kennel cough.
Bronchitis
Aside from wheezing, signs of bronchitis can include a dry hacking cough that is usually triggered by stress, exercise or direct physical pressure on the trachea. There may also be a fluctuating fever, retching or
gagging and passing of foamy saliva, intolerance to exercise, lethargy, a show of respiratory difficulty, and rapid breathing.
Obesity can be a complicating factor that could increase your dog's risk of bronchitis. Any dog is at risk, but small toy breeds and aging or older dogs can be more susceptible.
Infections
There are many symptoms to upper respiratory infections, including sneezing, coughing, nasal discharge and irritation, a low-grade fever, eye discharge, difficulty and labored breathing, loss of appetite resulting in weight loss,
exercise intolerance, snorting, wheezing and gagging. Puppies or older animals, unvaccinated pets, as well as dogs with impaired immune systems are more at risk to infections.
Parasites
If your dog is wheezing, coughing, losing weight, sneezing, has an increased breathing rate, nasal discharge, weakness,
lethargy,
vomiting, regurgitation, aspiration of stomach contents and food, or worms present in the feces, he may have a parasitic infection. There are many types of parasites that can interfere with your dog's respiratory tract and cause wheezing.