I have rcently been diagnosed with severe allergies and asthma, and have had sinus infections too. The most important step is to avoid the allergens, so it would be a good idea to have him tested. If he is worse at night, he might have dust mite allergies, and you need to case his bed and pillows in allergy barriers, and wash all bedding in hot water weekly.He should sleep in a bare room (no rugs, curtain, stuffed animals, etc.) with an air cleaner. The tests could tell you what else to avoid. There are very good medicines recently for dealing with asthma. I am sensitive to all animal danders, dust mites, several molds, and all kinds of pollen. Before I was diagnosed and learned what to avoid, the various allergens built up to a critical mass that twice left me hospitalized with allergic pheumonia. I have improved lately since I began taking rather large doses of vitamin C. Your son has been incredibly stressed by all his health problems (and perhaps by their cure). Since these things increase hsi need for nutrients, especially viatmin C, you might try getting staight vitamin C powder and stirring it into his juice or water. Make sure he is getting a good quality liquid vitamin formula, and avoid any kind of junk food. I also use licorice root tea and ginger tea to sothe the throat and keep down the mucus during attacks. Ginger might be too strong for an infant's taste, but licorice root would be tasty and well tolerated. Blessings on you both.