Mountain air is great, but we prefer to live in houses, and the air might not be so healthy in your house. These boxes that we live in protect us from the elements and assure us our privacy, but as we get better and better at boxing out the elements, we also box in lots of other things, like air pollutants. There are two categories of pollutants floating around in the air in your house: biological contaminants such as dust mites and mold, and chemical contaminants such as solvents coming out of building materials and furnishings. These are likely the cause of your symptoms. There are three steps to getting these things under control and maintaining a healthy atmosphere in your house. First, eliminate whatever sources of pollution you can by simply getting them out of your house: throw out moldy rugs and books; store solvents and cleaners outside; replace furniture, carpets, and underlay that give off odors and organic compounds with cleaner substitutes. (Rubber-based underlay in particular is a major offender.) Second, separate or isolate things you cannot eliminate. That might mean a coat of varnish on the underside of particleboard countertops. Then ventilate to lower concentrations of what is left by replacing polluted air with fresh air. With a little thought about the house we live in, we can greatly improve the quality of the air we breathe.