My daughter's pediatrician said she will not diagnose asthma until a child is 2-3 years old.  I have heard many times, in RT school perhaps, that the best way to diagnose asthma is by doing a PFT test, and a child under 2-3 cannot do it.    However, since asthma is genetic, if there is a long standing family history of asthma then asthma can be the "assumed" diagnosis for a child.  My daugher, for example, was diagnosed with asthma long before she was 2 due to asthma-like symptoms and the fact I have asthma.   I suppose the answer to your question is yes and no.  However, every doctor is different, and therefore this is something you may want to discuss with your child's pediatrician.