My 11th-month-old son had bronchitis when he was nine months old, his first time being sick. He had the bronchitis for one month and then he developed wheezing (x-rays showed interstitial pneumonitis). Physicians stated the possibility of him having asthma. An allergist saw my son for five minutes and diagnosed him with asthma. Is it possible to diagnose an infant with asthma the first time a child is sick and wheezes?
Your question is very common as more than 10 percent of infants and children do wheeze at some point in their childhood. With that first bout of wheezing, often triggered by respiratory colds caused by viruses, physicians tend to use "asthma-like" medicines to see if they help a child's breathing. Sometimes the meds do help, other times they don't. Parents, of course, then want to know whether this wheezing will ever happen again and, more pointedly, does this mean their child has asthma.
Asthma is really a clinical diagnosis. We see how a child acts with subsequent exposures to viruses and things known to trigger wheezing in kids. Whether "asthma-like" medicines make a difference with the amount of wheezing is also important. The more family members (particularly parents and siblings) with a history of allergies, the more likely the diagnosis. Eliminating exposure to cigarette smoke is always important.
Remember that wheezing does not necessarily mean asthma, and there is no simple, quick test that can be performed to make the definite diagnosis of asthma. Blood tests, chest x-rays, and measuring how much oxygen there is in the bloodstream are usually only helpful with treating the episode of wheezing at hand.
From what you've described, I wouldn't label your son yet. I would treat your son normally with the understanding that he may wheeze and need medication again in the future.