You need to be a detective. Double rinse all his clothes in hot water. Check everywhere in your house for mold and be aggressive about getting rid of even the tinest amt. Make sure that you don't use those plug in deodorizers because they are chemicals as well. Change your filter on the furnace and airconditioners frequently. Don't let anyone smoke in the house at all. Then talk to an allergist about eliminating some foods for awhile. Have you just put in new wall to wall carpet? Don't use chemicals to clean the rugs, only soap and water. Take down curtains and wash them. Eliminate things one by one. Good luck!