i don't know about humidifiers but i bet your son would benefit greatly from a nasal flush with a saline solution and few drops of 35% hydrogen peroxide. you will be amazed at how much doing this a few times will clean out his nasal passages and reduce swelling and calm allergies. do NOT use the 3% peroxide you buy at the drug store it is full of chemical stabilizers you don't want in your body. ONLY EVER use 35% food grade peroxide, either internally or externally. just remember to be very careful with the 35%, it is very powerful, use with exteme care. you can buy a neti pot to make it easier. even a simple saline solution flush will help.