My son was diagnosed with asthma around the same age - 18 months. Basically, a cold could progress to pneumonia quickly. Another unfortunate circumstance; asthma and allergies go hand in hand. He has year round allergies and carries an epi for allergies to certain trees and bees. The upside? He's 7 and has given himself the injections

Another upside; it could be worse.
He now does weekly allergy shots and takes it like a champ. He also graduated from the nebulizer to an inhaler recently as well. He carries his epi everywhere and understands why he needs it.