From the Pediatric Medical Center Allergy Handbook
Bronchiolitis is a viral upper respiratory tract infection that causes cold symptoms and wheezing in young infants. Various different viruses can cause bronchiolitis, but by far the most common cause is the respiratory syncitial virus (RSV). It occurs in outbreaks in the winter months, usually October to May.
Young infants with bronchiolitis typically have a runny nose, nasal congestion, cough and wheeze. The wheezing occurs because the virus affects the smaller bronchioles of the respiratory tract. They become inflamed and swollen. There is also increased mucus production which basically plugs the bronchiole. This results in the wheeze.
Older children and adults may become infected with the RSV. However, this causes typical cold symptoms. Because these individuals are older and much bigger, the bronchiole is also much bigger. Hence they do not become plugged, and there is no wheezing.
In asthma the bronchioles are narrowed, but this is because of an allergic reaction which causes the wall of the bronchiole to constrict. The end result is wheezing. In the treatment of asthma, bronchodilators are used to open up the wall of the bronchiole to allow free movement of air into and out of the lungs. This treatment may be beneficial for bronchiolitis even though the underlying disease process is very different from asthma.
Studies have shown that a large percentage of infants who have RSV-bronchiolitis go on to develop asthma later in life. Unfortunately, there is no way of predicting which infants will develop asthma. As a rule doctors are cautious in “labeling” a wheezing infant as having asthma, especially during the RSV season. Certainly is the infant does have asthma it will recur…time will tell.
From your history it sounds as if your son did in fact have bronchiolitis which responded nicely to the bronchodilators. Whether or not he will develop asthma is an issue that will be answered in time. I urge you to discuss this with your baby’s doctor so that all of your questions can be addressed. If anything, the doctor should be able to put your mind at ease.